I too use the SurpassII non pumped on my UCD, and I agree the performance is great. I've tried everything from a 14x6 thru a 16x4, and I felt the 15x4 (all APCs) provided the best static thrust for 3d flight. The plane flew regular aerobatics better on a 15x6 though. Plenty of power to hover and pull out as mentioned above. Not a rocket, but confident enough for low level stuff. I use Wildcat 10% in mine.