I like your username and your location, but mostly I like the info. I'm getting a new motor and after listening to the guys here I plan take the motor apart, port and polish, lap cylinder head & jug, re-gasket & replace all studs/nuts. I also thought about stainless steel used in conjunction with Heli-coil in threads. Like you say it's an aluminum casting and needs to be treated like real hard plastic. My question had more to do with heat transfer between the two metals, would the stainless get hotter/colder than the aluminum?
Too much heat is the biggest enemy to any engine, and from what I gather it really affects 2-stroke engines a lot. Don't forget those 4 long studs hold the whole shootin'match together & and any expansion/contraction here and performance is in the crapper