Wanted to add some take-aways;
1) I would use the 28mm railmaster that Naigon (Scott) recommends, for NBv3 people, I guess that translates to the 28mm premium from TCSS, although the railmaster is actually a different speaker
2) I'd have skipped the crystal chamber and used the G.O.T.H. padawan chassis instead. It would have saved a lot of headaches and still looked fantastic. The crystal chassis is fun, but ultimately, I'd have been just as happy without it.
3) Anyone following the G.O.T.H. DIY - wire your LED earlier in the build, waiting until the very end meant I had much less clearance to work with, whereas if I had done it earlier, I could have pulled wiring back toward the board before closing up the chassis
4) Clamp button users - dremel/drill/file a channel out toward your hole for the clamp. It will definitely make it easier to feed the wires when you're mounting the chassis to the grenade.
I'll add more if I think of anything else - I'm genuinely happy to be finished with this, but it might be a while before I undertake another haha.