I run 14x8 APCs on my ST 90 in a Midwest CAP 232, turned 9000 when it was still pretty new, believe it is higher now. Flies the plane very well....somewhat quiet by higher pitch and lower rpm, good speed for point rolls and knife-edge, and adequate vertical. Same results with a GP Extra 300 and a Magnum 91, the previous version. I don't do 3D or a lot of the hovering type stuff so you would want to go up in diameter and down in pitch if that is your thing....

Clair