I have it on head 3 on an 8/10, because I sometimes print black/darkest, then UB, then flash. But on a 6/8, I'd use head 2, because I'd expect to get most mileage out of a 1-Flash-Rest-(4)-(5)-6 combination. I think that would result in you revolving less often than if you put the flash in head 3.
(I'm not using a Gauntlet, but I doubt press type would affect this decision.)