Ok......
But FYI.....Most ameatures will have a "strong" grip from the get go...Most don't even know "why" the club is gripped the way it is or what is a strong / neutral / weak grip .......
Before I would tell someone to rotate thier grip...(without ever seeing them hit a shot) I would be more inclined to tell them to check thier feet shoulder and hip alingment....(that they are all going in the same direction)...I would bet that this guy has a "strong grip with a open stance"
Just rotaing the grip "stronger" likely will only hood the club at impact and now your looking at a pull slice....Again, the very "first" thing I would check before making ANY changes is his grip / stance / posture / alingment...not just grip....
Regarding the shaft....I completley understand that a weak shaft can leave a open club face at impact.... I also know that a too stiff shaft can flex / release / and be back on the flex again at impact ....neither are good, but this guy mentioned that he swings at 100mph tops....I am willing to bet that you won't find ANY clubfitter telling this guy to go to a stiffer shaft....especially if he wants any distance or ball height off the tee....JMO
BTW...what the hell am I doing talking about GOLF...I quit that racket....Golf is for sissys.........