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.