Thanks Sean. We designed them and had Gibson manufacture them using their external mufflers before running into the 4.5" pipes. At idle they are about three inches under water but just above the water line on plane. On my 36 I simply added Gibson turndowns onto the HPI external mufflers and they work just as good. In my opinion these are the only way to go if you want to comply with J2005 and still have some good performance left.

Dave, what kind of hp loss have you experienced with the new pipes?