S1 4.2 exhaust clearance

[phoenix]

Hi I am just fitting a new after market exhaust system which I am having trouble fitting. When offered up the twin centre boxes have the brackets at ninety degrees to the standard mounts on the body shell. Not a big problem as I took the mounts off and bent them so they are in the correct orientation to the exhaust system . but it is now only just clearing the heat shield . What is an ideal gap as I might have to make a short drop brackets .