RE: sundowner 50 or 80"?
I can't speak for the 50, but I had the 80" with a Moki 210. It was set up to best suggested CG on RCU threads and it still had a nasty snap in a moderately hard pylon turn. I attempted to twist and heat some washout in the tips but the wing structure was too stiff to yield good results. It needs a long runway to land if you don't have a head wind. After three sessions, I pull the engine and controls and sold it before I killed it.
Maybe I got a bad one or I expect too much.