The largest 2 stroke O.S. engine I have is the .75AX. I did not use that on the Big Stik, though the engine is very reliable.

I've found it much harder to deal with larger sized 2 strokers in terms of tuning, heating, etc.

So now that you mention it, I'm inclined to agree with you that there may be indeed a "sweet" spot for 2C engines in this range.

With larger 2C engines ( all non-OS so far ) I've typically had problems so I've ultimately gone with 4 strokers or gassers for engines above this range.