The problem I encountered was that the stock catalytic converter was too close to the floor, so I cut it out and welded in a small magnaflow cat. The design of my skid is very similar to Scotch740's (1/4 plate, angle iron reinforcements and the 33 Engineering mount). I cut a notch in the back of my skid for muffler clearance, as well as tweak the rear exhaust hangers to work with the slightly higher position. Loosening the flange before the muffler helps too, get it into position and tighten it up again, mine is pretty angled and doesn't leak. The bottom of the muffler is even with the skid.