Hi all; thanks for all the feedback. I just got off with phone with Rhett Allain (
http://www.wired.com/wiredscience/author/rhettallain/) - he is a physics professor and the friend-of-a-friend. He feels that the Magnus Effect can be effectively ignored in these foam basketballs because of their size, density, and low RPM of spin. Likewise, while air resistance will certainly be a measurable amount, it's exceptionally hard to calculate and also likely to be within the inconsistency of the machine itself in the best case scenario. This also means temperature, pressure, etc. can all be ignored.
Looks like you guys were right and I was wrong - no need to over-complicate it. This is good news for us though as the physics problem is now just one of projectile motion and nothing too nasty.
-Mike