Dirk,

My pal and I are running YS 91 FZs, his in a UCD and mine in a Kangke CAP Sport (but it will be in a UCD just as soon as my hobby shop guy gets one in). The UCD is a bit lighter, and of course much more agile, but the airplanes are about the same size. He is running a home-brew 20/20 blend, I'm running Cool Power 15%.

We've found that the best prop for our purposes is the APC 16x4W. We were running APC 16x6, but Dave Shadel advised that the static rpm we were getting was a bit too low for keeping the engine happy. I had thought the 16x4W was allowing the engine to overspeed, but no.

Anyway, this prop is amazing. It's like putting brakes on your model. Got a floater that just doesn't want to come down (i.e., a UCD without spoilerons on a calm day)? No problem. Chop to idle and watch that big boat paddle slow your plane down to a walk.

Acceleration is unbelievable as well. You will sacrifice some top end speed, but we're not flying pylon racers here. Even at that, you'll still be able to smoke most of the two-banger sport ships in the pattern. Plus, wide open it makes a really weird howling sound that will get everybody's attention.

Steve