Is your G15 at the stock 45.75"? Think any of the confidence with the Cleveland has anything to do with the slightly shorter length? (They're 45.25", aren't they?)
One of the guys I played with last weekend had the 270 I believe it was. He offered to let me hit it, but it was a 39 gram regular flex, so I had to pass.
He hit it pretty well though. His buddy had the R11 and must have tried 5 different hosel settings during the round.