Hi I have been out to have a look and the 70mm centre holes are at the rear with the sharpest angle at the top ,if you see what I mean. It will be great on the track and cheap as chips if you've got a couple of bits of alu kicking around.I did mine with a jigsaw and a file ,drilling both bits at once to keep the holes lined up. The chain does touch the exhaust but it's fine once your sitting on it. I hope this helps.