Randy I am about to order some motors for mine. We fly at 6200 ft elev and I have flowen a 17 lb bronco with two 91 our strokes and it flyes but nothing left. It is not a screamer by any means. We haven't lost a motor yet so I can't say what it would do. I know it would not maintain flight on one motor. I was thinking about 4 52 four strokes for power. There is nothing worse than flying a plane that is under powered. I can always throtal back.
I know there is a problem with prop clearance. 3 blades would help. What elevation do you fly at?
I would install flaps, up here they come in pretty hot. Thanks Rich