Mudsurfer,
The .80 is a nice engine but weights 22 oz. which is sort of heavy for this plane, a lot like putting a .61 on it. The Extra really flies well when it's kept light, .46's and .72's weight about 17 oz. which on a small plane like this can make a big difference.

The GP Extra is a GREAT flying plane and I think no matter what you do with it you will like the way it flies. We are just attempting to help out a bit with the experiences we have had flying them. The Saito is more expensive but worth every penny IMO. If you do go with the .80 you will probably have to relocate one of the servo's into the tail to get the plane to balance without adding lead. Like I said keep this plane as light as possible for maximum enjoyment and you can't go wrong with it.