I ordered your diffuser. I encourage you to make a new thread for your hardware mods to the keyboard and trackball, as they are very useful and informative, both to QMK and stock users.
My diffuser came in two layers, but I only ordered one. Was the second one included by mistake, or are they meant to be used in tandem? I’m using one layer right now.
I wrote this a bit ago:
The difference in light has been documented on-line but in person it really is night and day, and made me realize just how worn my keyboard silicone is! 
When the light was so muted it didn’t shine through the same way. Of course the light dispersion is much, much better than stock’s, as intended and as shown in the same pictures.
My uConsole keyboard has been used quite a bit. My roommate has a seldom-used console and in comparison my keypresses are much louder and my keyboard is much mushier. This diffuser brings both those qualities back towards stock; as you intended, the keys need less pressure, and are much quieter. It makes my device feel much more premium.
I have noticed two problems of which I think you should be informed. The first is that, on the keyboard, the domes are held in place by thermal masking (Kapton) tape that loses its adhesion over time. My right Alt key had that happen with the stock diffuser, and now your diffuser happened to push left Ctrl off as well. This is a very easy fix; remove the tape from the metal dome and replace it with new Kapton tape, which I successfully did for the second time yesterday. Ideally use a good-length strip as thin as the button itself, then flatten it against both sides of the button and the board so as to give the adhesive extra surface area for contact. The shinier side of the metal dome faces up. This isn’t the fault of the diffuser but just a natural symptom of age, and I can send pictures if anyone’s curious.
The second problem is that my diffuser’s affect on my typing pressure is inconsistent. I think it might be moving underneath the membrane; when I take it apart to check everything looks fine, but then when I put it back together like that the problem goes away. Select remains noticeably loud and mushy, also some other keys in its vicinity like ‘2’, ‘e’ (especially), ‘s’, ‘x’, and the modifiers, but the right side of the keyboard is still quiet. It’s all still fine and I have no desire to return the membrane.
All in all, thank you very much for this product! I look forward to trying your mod using a glass bead as the trackball next.