Adjusting Keycaps stem to go past the inner floor.

[Muramono]

Hello,

I am trying to make a flat (yes boring) keycap to use as a base to put a polished gemstone on top of the keycap. The issue I'm running into is that I want the keycap walls to sit far enough down on the keyboard without making them too long. To do this I would like to adjust it so that the stem can go further up/be taller in the direction of the top of the keycap. I understand the STEM_HEIGHT variable controls this, but I've noticed that if I increase this number too much it goes up into what seems to be a supporting layer/floor section that is between the top floor of the keycap and the stem section underneath. Is there anyway to move this supporting floor section between the stem and the top of the keycap up to create more space and allow the stem to extend further up into the keycap? I've included pictures zoomed in on this inside section that I'm talking about.

(Note when un-rendered it looks like the stem height is going through this extra floor section, but when rendered it is capped off at this section.)