For what it's worth...I have an 80" Midwest Extra 300XS that weights 15# 4 oz. (on wheels, I also fly it on floats!). It does everyhting that I'm capable of doing and does it well enough to make me look like a pretty decent pilot
I have a Moki 2.1 on it and couldn't be happier with the engine, including the ease of starting, power, idle, sound, etc. The rule of thumb with the Moki 2.1 is that it will burn about 1 ounce of fuel per minute of flying. My experience is that this is about right if you are running full throttle all the time - which I don't since it's not needed. The only time I checked the static thrust of the engine was when it was still pretty new - only about 1 gallon of 0% nitro fuel through it - and it was running rich with an APC 20x10 prop. Thrust was 19# at only 7200 RPM.