Problem getting the size of a MethodDesc

[cetio]

I've been trying to get the size of a MethodDesc for 3 hours, still can't figure out how to get it to work.
These are my MethodDesc structure fields:

    CodeFlags codeFlags;  // ushort enum
    ubyte chunkIndex; // equivalent to byte in C#
    ubyte methodIndex;  // equivalent to byte in C#
    ushort slotNumber;
    mixin(bitfields!(
        MethodClassification, "classification", 3,
        MethodFlags, "flags", 13,
    ));

And this is the code I'm trying to use to get the size of a MethodDesc:

        if (classification == MethodClassification.IL)
            return MethodDesc.sizeof + (hasNonVtableSlot() ? ptrdiff_t.sizeof : 0) // ptrdiff_t is equivalent to nint in C#
                 + (hasNativeCodeSlot() ? ptrdiff_t.sizeof : 0) 
                 + (hasMethodImpl() ? MethodImpl.sizeof : 0);
        ... this repeats for each MethodClassification

I'm getting a size of 24 for a MethodDesc that has the classification IL and has a native and non-vtable slot, when adding this to the pointer of the first MethodDesc in the MethodDescChunk I get a pointer to a constructor descriptor. The size of the new MethodDesc returns 40. When adding 40 to the new pointer I get an invalid pointer, so obviously I'm doing something wrong.
Also, every MethodDesc returns IL as its classification, so I didn't find it relevant to post the other structures.