I flew a SIG Four Star 60 with a Magnum .91RFS, prop'ed with a MA 13x8 three-blade. It was amazing! I swapped props for a 14x6 and the place flew like a sleepy elephant- no vertical, no straight-and-level speed. It actually went DOWN in performance, both vertical and speed. It would BARELY hover with the two-blade 14x6, and could climb out of a hover with the three-blade 13x8. I found that with the right three-blade prop performance was better than the recommended two-blade prop.

Lachlan