Was the smallest size to cut a com before its not usable in a trinity 21 turn spec motor

Or instead of being not usable I guess i should have said wants the smallest before performance would start to diminish

The rule-of-thumb so to speak for almost all comms is .270. But most motors tend to run their best around the .280 or so. If you have a dyno, then check it after a really good run, and just try to get the same #'s out of it or better. Just my 2cents worth.
Kevin