RE: Best/Fastest Plane for a Moki 2.10 !?!?
Speed is good, but how fast do you want to fly, IOW how fast do you expect that Moki can pull something? Potential speed is directly proportional to pitch and rpm, without those all the horsepower in the world isn't much good. The highest pitch I have seen in APC's lineup is 14". At 10,000 rpm, 1000rpm over the mfg rating for the engine, that is good for 133mph. That is about how fast a low cost .46 with a tuned muffler will pull a delta or Q500 airframe.
So you need to decide what you actually are looking for in terms of speed. This is indeed the issue with the bigger engines - they are not generally designed for much higher rpm than that, being set up for sport, aerobatic and scale use, with the attendant manners and broad torque range. So couple such an engine with the highest pitch prop you can find that it will spin, and you can still be whupped by a sport .46 on a $75 airplane. Now, I'm not saying that 130mph or so isn't fast, it is pretty quick - just don't expect to start trouncing the ARF quickie 500's at the local field anytime soon with that engine. My guess is you will have to work to exceed 120-125mph or thereabouts. Unless you start hand-carving 12x16 props or something.
MJD