> It's probably pict3d's fault, but there's no indication of this module being of "pre-alpha" stability. Or maybe it's an interaction with Racket-on-chez and C library interfacing.

Racket-on-Chez is what's pre-alpha. I don't think there's been requests for anyone to test it unless they were going to dig into the guts and try to fix things.

> since 3d is an application that needs speed

if the slowest part of your 3D is how quickly you can make calls into OpenGL, you're in a pretty good place.