I would not cut the cowl ring, since the cowl slides on in a lower postion then slides up on the lower tabs will allow you to cut the pipes. Simply put the cowl on but dont slide it up, measure the distance from the bottom of the fuse to the top of the cowl ring at the bottom, this is the maximum length they can be to pass the cowl ring. Then you can install the muffler measure down and keep as much of the pipes as you can but still miss the cowl ring. You can then cut the bottom of the cowl to allow the pipes to exit along with geat through the bottom of the cowl. Such as this, http://www.rcuniverse.com/forum/fb.asp?m=4541104 hope that helps some.