I had a Magnum 91 4 stroke in mine; in retrospect my OS 70 has equal or better power than the 91 but I didn't have the 70 when I got the Matrix. I still have it but it's been decommissioned for now. My main suggestion is do not use the stock elevator setup. Use dual elevator servos in the tail. When I'm ready to fly mine again that is what I will do. Also, and OS or Magnum 91 is just not a good choice for 3D - the saito 82, Os/Magnum 70 or the obvious YS options.

Flight performance? Handles wind well, very good control authority but does show quite a bit of wing rock upright in a harrier - Inverted isn't as bad. It is a nice airplane and I have enjoyed mine. I think when I get better - it will be better.