I'm 90% sure that's the Goldberg Anniversary Cub with an after-market landing gear. It's the best one IMHO. Too bad they built it with the full-size wing.

You can put a 65 on it, but all that will achieve is to make it go higher. That is a lot of wing to get any speed out of.

You can lower the mount, but that will only create more "Up" pull on top of all that lift