In doing a little experimenting a friend and I converted a 33cc Homelight chainsaw engine and installed it on his 120 Stinger. Here is what we came up with.

Weight: 4lbs (almost dead even)
Came with a BIG carb so no worries about fuel!
Turned a 16/8 APC over 10000 (let off before we damaged the engine!) No load on the engine at all!
Ended up doing the first flight (& the 2nd 3rd so forth) with a wood 18/8 and it turned the prop at 8100. We didnt have an APC this size at the time but we are going to get one. Would probably add a few hundred more.
But anyway the plane performed GREAT! After a few flights to give the engine a little run time we actually experienced hovering & unlimited vertical out of a converted engine.
If you would like to hear it from the owner him self or info contact me.
Best of all - Cheap to buy, Cheap to fly!