David, I love the graphics!
Mine will maintain a hover with the 91fs, but it won't pull up. I didn't enlarge the tail as I'm not really into 3D stuff. Being completely "stock", it flies conventional aerobatics very nicely. Mine weighs 7lb 13oz.
I'm also using a 14x6. If you have better luck with the 15", let me know.
And I don't care what anybody else thinks. The Great Planes kit looks WAY better than the Goldberg.
Tom