I run a 12x7 prop on an OS 70

And given a choice between using a 70 /4 or a 46/2 on an Extra 300, I'll take the 4-stroke every time.

And while a 4-stroke MAY require an occasional valve adjustment, I have had about 12 of them over the past 15 years, and I have had to adjust valves once.

Also, I run them on Cool Power 15% and never use after run oil. Again, with 12 engines, over 15 years, I've had to replace bearings once.