I would not use the friction modifier to an automatic unless it was needed. It did help resolve the lock up converter chatter on some cars so it is not unheard of, but not really advisable if not needed.
As for mixing type F fluid with Mercon (synthetic or not) and using it in a trans that was designed for Mercon, that is automatic transmission homicide. Type F will not provide sufficient lubrication for clutches that were not designed for it. Anyone who does this is at extreme risk. (Don't ask me how I know because I'm NOT TELLING. Let's just say I learned the hard way.
