I just did 4 flying runs on my new zen-50. With a 50SX running a bolly 11.5x6 prop without nitro, i couldnt gety any power. is is cz theres no nitro in the fuel or is id due to the lack of a tune pipe? THe aircraft flies extremely heavy. I cant make out for the cg being rt or wrong.In Inverted flight it comes down on the nose. In knife edge it comes towards the canopy n big time!! The engine's revving high n u can tell that its the max power u can expect from this engine. One more thing, the retracts suck! either they bend or one of them doesnt lock. What do i do?