@Flight Detent.
Could it be a case of a simplified set of performance calcs (or charts more likely) which don't have provision for any "special" flex calcs?
So the option of your second sentence might not exist - my only choices are the FULL set of OAT performance or the FULL set of FLEX temp performance - no mix and match.In that case, since I have to account for the full thrust scenario, I have to pick the more conservative set, and use that?