Hey, thanks again for replying. I did use the Deskey stab pads for their intended purpose rather than for the mod.
So what I did last night was assembled a clean Durock v2 stab (no lube or mod) and used that on the Backspace (with Deskey stab pad). Seemed fine. Slightly sunken compared to the surrounding keys (with both the Drop and Corsair keycaps), but barely noticeable and far less sunken than before (with mod). It felt normal otherwise, pressed fine, bounced back fine, etc. So then I lightly lubed it the way a bunch of tutorials suggested, still seemed good and rattled a little less -- great. So I then unmodded the other ones (left-Shift, Spacebar, Enter), meticulously cleaned them, and assembled them the way I did with Backspace. Everything seemed fine, so I assembled the rest of the board.
As I was putting the keycaps on, I noticed backspace, left shift, and enter sunk slightly more than without the case on it, but still felt good. Spacebar was suddenly mushy again. The weird thing? If I do the upside-down spacebar, it's not mushy anymore. If I put it back to normal, it's mushy.
Edit: Just disassembled again and did some troubleshooting. The silicone pad is restricting the stab wire of the spacebar. Not sure why or really what to do about it. Never heard about that happening on the KBD67 Lite.
Any ideas? As always, thanks for helping!