Thanks Spike for your speed-light fix, you're the best, really!

But unfortunately bug it's still there

Model still disappears and re-appears when turning around it. I took a look at your modified files but I didn't understand which file is the culprit one.
PS: What abou Bullet integration, did I see right?
EDIT: my map is q3bsp, I noticed that you modified gl_q2bsp.c. Could that be the problem?