I've been playing Wing Commander 1 and 2 (and having a blast), and I've noticed that when there's lots of enemies flying around, or when somebody fills the screen, there's a massive slowdown. Any ideas what's causing the slowdown?

Yes the multiple objects on screen. WC1 is easier to find a good setting for (roughly 5000 cycles) but WC2 can be trickier. On my own machine I set it to 5300 cycles. It's a fair balance between not being too fast with 1 fighter on screen and not too slow with more than 5.

I've got WC1 set for 6000 cycles. Still slows way down. WC2's slowdown with lots of activity going on at the waypoint (in particular with 4 or more Kilrathi blazing away), still causes lots of slowdowns. Never had this problem when I was playing WC2 on an actual 486 computer.

Guess lots of fiddling is needed...

Small update: Setting WC2 to 20000 cycles solves the massive slowdowns in flight, even if it causes the animations to be a little on the fast side. Setting WC1 to 20000 made the game too fast (even in flight). Perhaps 10-15000 cycles will help that. Must experiment more.