Had to do that on the SuperTrapp that I gave Sluggo when we fitted it up. Seems to be some variation in the amount the inner pipe protrudes past the ring that seals the inner and outer pipes. His is a newer model than the 96 I bought it for and it worked fine on mine. I just ended up going another way at the time. Still have an Aluminum Honda 500 version of a Trapp sitting in a box for when this HD one dies, assuming it will in time like the first 1/2 of the pair did. IMHO the one that fits the easier is the HD FXD/F (I think that is Dyna Wide Glide model, stacked mufflers on the RH side like a sportster, and with the almost 1300cc engine which makes the flow rate correct for our 650 cc ) version as it is slotted for the mount and a carriage bolt work well. Max

Include how using a grinder to shorten the header can be hazardous. The sparks past the battery vent tube can ( & WILL) ignite the hydrogen, popping the battery case. You KNOW how I know this..