I'm drawing from my IMAC experience here but I will agree that flying the back of the box gives you more time. I have also seen guys flying the lower classes using too much power between manuevers.

As for the caller, memorize your sequences so you can fly it without a caller. Then when you are in a contest situation your caller can coach you on things like speed, box depth, positioning and not have to tell you a laundry list of manuvers.