I am having good luck with an OS 61 FX and a 13-6 prop. This combo will hover at a little over half throttle. CG is more critical than than overall power. I installed a servo under the bottom of the fuse for a short pull-pull rudder control and I still had to add some tail-weight to get the CG back to 4 1/2". My OS 61 FX with muffler weighs 24 oz. I wouldn't go with anything that weighs more as there is not much room to move the battery around.