Well this took the better part of my two days off, but maybe I’m just really slow. I did find that there was quite a bit of movement with the Niz housings in my plate before full assembly so I went ahead and applied the electrical tape as hi-xxi suggested, just in case. Unfortunately while assembling the costar stabs I realized that I don’t have any spare keycap sets. 
I have a couple sets on order (MT3 Serika for this board), but I might have to grab another set in the meantime.
The combination of Des rings with the Niz switches has no squeaking like there was with the Silence-X rings in the stock topre switches. I’d definitely recommend generous amounts of lube for the costar stab as mine was still fairly rattly with a small amount of dielectric grease.
