I've been flying what's usually called a 120 size scale aerobatic plane. It's a Goldberg Sukhoi (72" span 10.5 lb). It seemed huge when I was building it but still uses "conventional" R/C airplane construction and details. It seems about as big as you want to go with glow power.

I'm playing around with the idea of stepping up to the next size and using gas power. I would probably be looking at a 27% model with a 40cc engine. A Midwest Cap with a ZDZ40, for example. So, I have a few questions:
*Will I be able to tell the difference in flight characteristics between a 72" span and an 80" span model?
*Is an 80" model usually considered "giant scale"?
*How much new technique and equipment set-up will I have to learn?
*Is there a large price jump when going from something like the Goldberg Sukhoi to a Midwest Cap?
*Are redundant battery systems used in models of this size?
*Are dual servos used on elevator, rudder, and ailerons?
*Is an 80" model still OK for moderately sized fields?

Any other comments or words of encouragement (or warnings of reality) greatly appreciated.