http://www.dual-boxing.com/showthread.php?t=25491

That thread describes how to "sync" your camera positions. Then you just need to line up your toons as well as possible. It'll never be perfect.

Then, I use the manual camera view settings as that thread describes to make sure they're all looking the same way/angle and as long as you aren't at max range, it usually works good enough to be viable.