SRT, you're pushing this into a YS vs. DLE discussion that will stretch on forever, and I'm not going there. You said you thought the plane was too small for a gas engine. I'm saying I think not, period. I fly 20 powered stuff this size and weight all the time. At 9 lbs, the 20's can easily pull a plane out of a hover. I'd say that's plenty of vertical performance for most people.
I think the better question might be regarding whether a YS115 or 20cc DLE/RCGF/Valleyview might not be a bit much for a lot of flyers. They'll definitely be in the "over the top" category. If you are used to flying hot rod sport planes, these engines might be a good choice. I think a 16x8 would be a poor choice for a prop though. A 17x6 would help keep the plane slowed down to the point where it has a much better chance of keeping it's critical control surfaces where they are intended...... and still be plenty fast. I don't think this plane will do well at 80 mph plus.