I've heard that it's harder to pull the the trim lever with a longer nozzle. It would force your ski around harder though, for both flips and rolls. I'm looking at one of those nozzles for my x-metal trim. I was thinking no more than 20mm, but I don't have personal experience with it, so take this as advice, not the definite way to go. Personally I'd rather have a stock length nozzle with a vertical vane to turn harder, but not make it any harder to pull the trim lever.