If you don't have any luck with Jamie or Bob, try Steve Baker. The RLV 5507 is what you need if you are using a 15 degree mount. The 5511 ( which I'm sure Steve would have ) fits similar to the 5507, but I don't know if you will be allowed to use it. Neither pipe will work with a flat mount. Paul Rice designed a pipe 5517 that RLV made for us last year. It is the only one that fits the flat mount setup.