The OS 91 will be plenty of power. It wont 3D with authority put it will have unlimited verticle.

I have had one for over 2 years flying with a ST90 with jett muffler. Its a fantastic flyer.

To get the most out of it you need to get good servos. Mine has futabab 9202 on elevator and rudder and 9001 on ailerons. I fly mine for F3A practice and have minimum throws on mine.

I went pull-pull on rudder and elevator.

The only negative I can see is how the cowl is setup. Its hard to install well. I ended up reinforcing the inside of the cowl with ply and then built brackets on the front of the plane to mount the cowl to. Let me know if you would like some pics.