I am flying the fx and it does fly very well. I have the eflite 400 outrunner and it does hover well, but does not pull out as fast as I would like. Also Knife edge flight on this one is not as stable as say the eflite yak 54, or the eflite profile Ultimate. The FX wants to tumble toward the belly on right rudder. I am using kokam 1500s and thunder power 1350.
It does very well in most aspects but anything complex using rudder seems to get an F in my book.
I am going to check out extra stiffy. From what I hear getting one seems to be the only prob. 3DAP