i just put on a sbp expansion chamber yesterday, although it fits its a tight fit and i'd like it a little more secure. i messed around with adjusting it for 2 hours trying to get the best fit but its not quite where i would like it. i want to know if its ok to take off about an inch on the J pipe and how it will potentially effect performance on a 80cc. this is all on a 29'' mountain bike with a few other mods.