Minimum cowl to exhaust clearance

I have a 6A polyester cowl and Vetterman's crossover exhaust with mufflers.
In doing the final assembly of the engine compartment I still have some areas where the exhaust system is very close to the cowl, almost touching, especially in the muffler/heat muff area.

It was a real struggle to get things to this point. I still have some cowl painting and reflective shielding to put on the cowl.

How much clearance should I try to get to minimize or alleviate heat damage to the lower cowl?

Dave A.
6A

Not only heat damage, but the engine will move on the mounts at start up and shut down, so if you don't have enough clearance those parts will hit the cowl. I don't know the precise answer to your question - hopefully some others can chime in with a rule of thumb.