I've never had a problem with greying out or blacking out on any coaster, but I would suspect that if you grey out on a 50 deg. incline, or whatever a traditonal Boomerang is, that it would probably be -more- likely to happen on a 90 deg. incline ! 
 
Personally, I'd take the chance.  V2 rocks, 
and greying out can be fun, right ? ;) 
 
(seriously though, if you are concerned, and you don't like greying out, you might want to hold off - or better yet - talk to your doctor and see what the reason is, and what you can do about it) 
 *** This post was edited by Joe Carroll on 5/30/2001. ***