I've got a Hangar 9 spitfire w/a Saito .91 on it and 13x8 was the way to go for it. I've got a Showtime 90 too with an Evolution 1.00 in it and it is awesome, it does that 30% hover thing easily and flies like its on rails. Reinforce the landing gear!!!!!! It isn't held in the fuselage by much at all and any little bump could take it out. I lost mine on my fourth flight after a 8" bounce on landing.