I just flew my UCD3D today (3 flights) and it flew great! I have an OS 91 pumper in it with a 14x6 prop. (will try a 15x5 once broken in a little more) This is what they (GP) recommmends so I went with it. It balances out excellent,... about 5" (4.75-5 recommended). Even with this new 91 pumper (ran three tanks through for break-in), it has PLENTY of verticle power. If you want to send it to the moon, use something bigger. Hovers excellent with plenty of pull-out power. I flew this plane mostly at 1/3 throttle and it is a ball! It is not a fast plane by any means (as designed). Nice slow landings too... Plenty of reaction time, even more than my Falcon 56 trainer! Can't wait to fly it again as I still need to iron out a few coupling issues (mainly with KE,... it tend to pull to belly of plane). The fuel tank is installed as per the instructions. I might move it above CG to see what that does.

A VERY FUN plane nevertheless !