Quote Originally Posted by Dana View Post
A related issue I've been wondering about is aerobatics. I'm designing an aerobatic ultralight which will probably use a 447 or similar. I'd hate to have the engine seize coming out of a hammerhead or loop. The aerobatic Quicksilver Super used a 503 (with diaphragm carburetor) and I haven't heard of problems with it, though many 503's had oil injection.
More anecdotal evidence perhaps but seems like one could examine the engine failures on Rans S-9's and S-10's as they are purposely designed for aerobatics and have reasonable service history available and compare to the straight and level fleet.

I considered the same thing once, installing a two-stroke on something like a Baby Lakes. Outside the relatively low "TBO" I think it would perform satisfactorily but you can almost bet the bank on a power off landing in a relatively high wing load airplane at some point.