I'm currently flying the 40 size US, and it is a BLAST!! I have a Thunder Tiger 46 pro in the nose, and I needed to move the battery pack to behind the servo tray for balance, but other than that it's been great...just enough power to hover up here in the high country of New Mexico. The only problem I've had is the tail gear, the one that comes with the kit is junk, it broke after 3 easy landings...get a good quality tail gear, like a Sullivan, and you'll have no problems. I have a Saito 72 to put into the plane, but right now it's in a Sig Somethin' Extra, and I'm having too much fun with it to take it out...fun is that Name of the Game!!!