Yeah, it is definitely not known for being a powerhouse, but it fits a lot of scale cowls so nicely. That's why I did mine for in my Tiger Moth biplane. Nothing sticks out of the cowl and that looks so much better!

A larger carb should definitely help. You could also trade off a little static thrust for speed by going to a 16 x 8 prop on it for now; until it breaks in. That lessens the load a bit and makes it a little easier for the engine break in, especially in a cowled situation where it might try to run a little warm. I doubt you do much hovering or other 3D antics with this ship, so you might like the 16 x 8 in any case as you won't miss the lost thrust, and the extra speed offered by that prop will allow you to throttle back and cruise, and make a high speed pass when you want to do so. Most people use about an 18 x 8 on this engine, but it never hurts to experiment until you come up with a combo you like. Just keep it under 8000 rpms. It may turn the 16 x 8 more than that once it's got a bigger carb and is broken in.

Another thing is the brand of prop. An APC prop is more efficient and what I normally run on everything. It's just that on my big Fokker and Tiger Moth, the wood props look so much nicer....

AV8TOR