diff --git a/src/libpisp/backend/backend.cpp b/src/libpisp/backend/backend.cpp
index edf3cc1..26fdde5 100644
--- a/src/libpisp/backend/backend.cpp
+++ b/src/libpisp/backend/backend.cpp
@@ -23,7 +23,6 @@ BackEnd::BackEnd(Config const &config, PiSPVariant const &variant)
 	if (config_.max_tile_width > max_tile_width)
 		PISP_LOG(fatal, "Configured max tile width " << config_.max_tile_width << " exceeds " << max_tile_width);
 
-	smart_resize_.resize(2, { 0, 0 });
 	smart_resize_dirty_ = 0;
 
 	const char *env = std::getenv("LIBPISP_BE_CONFIG_FILE");
diff --git a/src/libpisp/backend/backend.hpp b/src/libpisp/backend/backend.hpp
index cb5a4d2..0d572d3 100644
--- a/src/libpisp/backend/backend.hpp
+++ b/src/libpisp/backend/backend.hpp
@@ -7,11 +7,11 @@
  */
 #pragma once
 
+#include <array>
 #include <cstdint>
 #include <string>
 #include <type_traits>
 #include <utility>
-#include <vector>
 
 #include "common/shm_mutex.hpp"
 #include "tiling/pisp_tiling.hpp"
@@ -24,6 +24,13 @@
 namespace libpisp
 {
 
+using TileArray = std::array<pisp_tile, PISP_BACK_END_NUM_TILES>;
+
+// We use std::array<std::pair<.,.>> insead of std::map<.,.> to ensure this object provides a standard layout.
+using YcbcrMap = std::array<std::pair<std::string, pisp_be_ccm_config>, 16>;
+using ResampleMap = std::array<std::pair<std::string, pisp_be_resample_config>, 16>;
+using ResampleList = std::array<std::pair<double, std::string>, 16>;
+
 class BackEnd final
 {
 public:
@@ -51,8 +58,8 @@ class BackEnd final
 
 	struct SmartResize
 	{
-		uint16_t width;
-		uint16_t height;
+		uint16_t width = 0;
+		uint16_t height = 0;
 	};
 
 	BackEnd(Config const &user_config, PiSPVariant const &variant);
@@ -165,7 +172,7 @@ class BackEnd final
 	void finaliseConfig();
 	void updateSmartResize();
 	void updateTiles();
-	std::vector<pisp_tile> retilePipeline(TilingConfig const &tiling_config);
+	TileArray retilePipeline(TilingConfig const &tiling_config);
 	void finaliseTiling();
 	void getOutputSize(int output_num, uint16_t *width, uint16_t *height, pisp_image_format_config const &ifmt) const;
 
@@ -178,18 +185,17 @@ class BackEnd final
 	pisp_image_format_config max_input_;
 	bool retile_;
 	bool finalise_tiling_;
-	std::vector<pisp_tile> tiles_;
+	TileArray tiles_;
 	int num_tiles_x_, num_tiles_y_;
 	mutable ShmMutex mutex_;
-	std::vector<SmartResize> smart_resize_;
+	std::array<SmartResize, PISP_BACK_END_NUM_OUTPUTS> smart_resize_;
 	uint32_t smart_resize_dirty_;
 
 	// Default config
-	// We use std::vector<std::pair<.,.>> insead of std::map<.,.> to ensure this object provides a standard layout.
-	std::vector<std::pair<std::string, pisp_be_ccm_config>> ycbcr_map_;
-	std::vector<std::pair<std::string, pisp_be_ccm_config>> inverse_ycbcr_map_;
-	std::vector<std::pair<std::string, pisp_be_resample_config>> resample_filter_map_;
-	std::vector<std::pair<double, std::string>> resample_select_list_;
+	YcbcrMap ycbcr_map_;
+	YcbcrMap inverse_ycbcr_map_;
+	ResampleMap resample_filter_map_;
+	ResampleList resample_select_list_;
 	pisp_be_sharpen_config default_sharpen_;
 	pisp_be_sh_fc_combine_config default_shfc_;
 };
diff --git a/src/libpisp/backend/backend_default_config.cpp b/src/libpisp/backend/backend_default_config.cpp
index b0163b7..3286d89 100644
--- a/src/libpisp/backend/backend_default_config.cpp
+++ b/src/libpisp/backend/backend_default_config.cpp
@@ -133,10 +133,11 @@ void initialise_gamma(pisp_be_gamma_config &gamma, const json &root)
 	}
 }
 
-void read_resample(std::vector<std::pair<std::string, pisp_be_resample_config>> &resample_filter_map,
-				   std::vector<std::pair<double, std::string>> &resample_select_list, const json &root)
+void read_resample(libpisp::ResampleMap &resample_filter_map, libpisp::ResampleList &resample_select_list,
+				   const json &root)
 {
 	auto &filters = root["resample"]["filters"];
+	unsigned int i = 0, j = 0;
 
 	for (auto const &[name, filter] : filters.items())
 	{
@@ -148,22 +149,28 @@ void read_resample(std::vector<std::pair<std::string, pisp_be_resample_config>>
 			throw std::runtime_error("read_resample: Incorrect number of filter coefficients");
 
 		memcpy(r.coef, coefs.data(), sizeof(r.coef));
-		resample_filter_map.emplace_back(name, r);
+		resample_filter_map[i++] = { name, r };
+		if (i == resample_filter_map.size())
+			break;
 	}
 
+	i = 0;
 	auto &smart = root["resample"]["smart_selection"];
 	for (auto &scale : smart["downscale"])
-		resample_select_list.emplace_back(scale.get<double>(), std::string {});
+	{
+		resample_select_list[i++] = { scale.get<double>(), std::string {} };
+		if (i == resample_select_list.size())
+			break;
+	}
 
-	unsigned int i = 0;
 	for (auto &filter : smart["filter"])
 	{
-		resample_select_list[i].second = filter.get<std::string>();
-		if (++i == resample_select_list.size())
+		resample_select_list[j++].second = filter.get<std::string>();
+		if (j == resample_select_list.size())
 			break;
 	}
-	if (i != resample_select_list.size())
-		throw std::runtime_error("read_resample: Incorrect number of filters");
+	if (j != i)
+		throw std::runtime_error("read_resample: Incorrect number of smart filters/downscale factors");
 }
 
 // Macros for the sharpening filters, to avoid repeating the same code 5 times
@@ -222,10 +229,10 @@ void read_sharpen(pisp_be_sharpen_config &sharpen, pisp_be_sh_fc_combine_config
 	shfc.y_factor = params["shfc_y_factor"].get<double>() * (1 << 8);
 }
 
-void read_ycbcr(std::vector<std::pair<std::string, pisp_be_ccm_config>> &ycbcr_map,
-				std::vector<std::pair<std::string, pisp_be_ccm_config>> &inverse_ycbcr_map, const json &root)
+void read_ycbcr(libpisp::YcbcrMap &ycbcr_map, libpisp::YcbcrMap &inverse_ycbcr_map, const json &root)
 {
 	auto encoding = root["colour_encoding"];
+	unsigned int i = 0;
 
 	for (auto const &[format, enc] : encoding.items())
 	{
@@ -247,15 +254,17 @@ void read_ycbcr(std::vector<std::pair<std::string, pisp_be_ccm_config>> &ycbcr_m
 			memcpy(ccm.offsets, offsets.data(), sizeof(ccm.offsets));
 
 			if (key == "ycbcr")
-				ycbcr_map.emplace_back(format, ccm);
+				ycbcr_map[i] = { format, ccm };
 			else
-				inverse_ycbcr_map.emplace_back(format, ccm);
+				inverse_ycbcr_map[i] = { format, ccm };
 		}
+
+		if (++i == ycbcr_map.size())
+			break;
 	}
 }
 
-void get_matrix(pisp_be_ccm_config &matrix, const std::vector<std::pair<std::string, pisp_be_ccm_config>> &map,
-				const std::string &colour_space)
+void get_matrix(pisp_be_ccm_config &matrix, const libpisp::YcbcrMap &map, const std::string &colour_space)
 {
 	memset(matrix.coeffs, 0, sizeof(matrix.coeffs));
 	memset(matrix.offsets, 0, sizeof(matrix.offsets));
diff --git a/src/libpisp/backend/backend_prepare.cpp b/src/libpisp/backend/backend_prepare.cpp
index 689fa19..13accb0 100644
--- a/src/libpisp/backend/backend_prepare.cpp
+++ b/src/libpisp/backend/backend_prepare.cpp
@@ -304,12 +304,13 @@ void finalise_output(pisp_be_output_format_config &config)
 		throw std::runtime_error("finalise_output: image stride should be at least 16-byte aligned");
 }
 
-void check_tiles(std::vector<pisp_tile> const &tiles, uint32_t rgb_enables, unsigned int numBranches,
-		 TilingConfig const &tiling_config)
+void check_tiles(TileArray const &tiles, uint32_t rgb_enables, unsigned int numBranches, unsigned int num_tiles,
+				 TilingConfig const &tiling_config)
 {
-	int tile_num = 0;
-	for (auto &tile : tiles)
+	for (unsigned int tile_num = 0; tile_num < num_tiles; tile_num++)
 	{
+		const pisp_tile &tile = tiles[tile_num];
+
 		PISP_ASSERT(tile.input_width && tile.input_height); // zero inputs shouldn't be possible
 
 		if (tile.input_width < PISP_BACK_END_MIN_TILE_WIDTH || tile.input_height < PISP_BACK_END_MIN_TILE_HEIGHT)
@@ -361,7 +362,6 @@ void check_tiles(std::vector<pisp_tile> const &tiles, uint32_t rgb_enables, unsi
 					throw std::runtime_error("Tile height too small at output");
 			}
 		}
-		tile_num++;
 	}
 }
 
@@ -729,7 +729,8 @@ void BackEnd::updateTiles()
 		// outside the actual image width (and we've chosen not to handle compression like that).
 		tiling_config.compressed_input = false;
 		tiles_ = retilePipeline(tiling_config);
-		check_tiles(tiles_, c.global.rgb_enables, variant_.BackEndNumBranches(0), tiling_config);
+		check_tiles(tiles_, c.global.rgb_enables, variant_.BackEndNumBranches(0), num_tiles_x_ * num_tiles_y_,
+					tiling_config);
 		finalise_tiling_ = true;
 	}
 
@@ -740,7 +741,7 @@ void BackEnd::updateTiles()
 	}
 }
 
-std::vector<pisp_tile> BackEnd::retilePipeline(TilingConfig const &tiling_config)
+TileArray BackEnd::retilePipeline(TilingConfig const &tiling_config)
 {
 	// The tiling library provides tiles in a SW Tile structure.
 	Tile tiles[PISP_BACK_END_NUM_TILES];
@@ -750,11 +751,11 @@ std::vector<pisp_tile> BackEnd::retilePipeline(TilingConfig const &tiling_config
 	num_tiles_x_ = grid.dx;
 	num_tiles_y_ = grid.dy;
 
-	std::vector<pisp_tile> tile_vector(num_tiles_x_ * num_tiles_y_);
+	TileArray tile_array;
 	// Finally convert the Tiles into pisp_tiles.
 	for (int i = 0; i < num_tiles_x_ * num_tiles_y_; i++)
 	{
-		pisp_tile &t = tile_vector[i];
+		pisp_tile &t = tile_array[i];
 
 		memset(&t, 0, sizeof(pisp_tile));
 		t.edge = 0;
@@ -892,14 +893,16 @@ std::vector<pisp_tile> BackEnd::retilePipeline(TilingConfig const &tiling_config
 			}
 		}
 	}
-	return tile_vector;
+	return tile_array;
 }
 
 void BackEnd::finaliseTiling()
 {
 	// Update tile parameters (offsets/strides) from on the BE pipeline configuration.
-	for (pisp_tile &t : tiles_)
+	for (int i = 0; i < num_tiles_x_ * num_tiles_y_; i++)
 	{
+		pisp_tile &t = tiles_[i];
+
 		calculate_input_addr_offset(t.input_offset_x, t.input_offset_y, be_config_.input_format, &t.input_addr_offset,
 									&t.input_addr_offset2);
 		calculate_input_addr_offset(t.input_offset_x, t.input_offset_y, be_config_.tdn_input_format,