I'd say the ailerons and elevator are OK without modification. I'd add some area to the rudder instead. You'll need it if you want to hover. If nothing else, definitely strengthen the area where the landing gear mounts by replacing the balsa outer skin with light ply. That area is notoriously weak on the Fun 51 / Extra Special.

It's not the hovering machine that the Burrito is, but it's still a blast to fly. You wil love it. The Magnum 51 is a lot of engine for the Fun 51. Mine weighed just under 4 lbs with an Enya 45SS. You will go vertical like a rocket.