There's very little difference between a 281 and 288 in real world cutting.
The 660s were pigs
But I did run a nice 066 before.
I was hoping getting from 81cc to 88cc would bring it close enough to 92cc (066) that the saw would be in the ballpark. I guess there's more to it than that. I do know these things are pretty high compression saws (close to 200#).