I just got back from the maiden flight of my predator II with a GMS .25. The plane flew absolutely perfect, smooth and tracked like it was on rails, but with this engine no faster than the average sport plane. I plan on entering the SLow Quickee race that my local flying field puts on, so I'm pretty much stuck with the .25 sized engine. One problem I noticed was the plane would torque over to the right in the verticle and with the V-tail I was not able to to stop this without inducing roll.