How to keep paint from burning

On my 37 chevy truck I made a roll pan on the rear and made two cutouts for the exhaust system. I now want to redue the same roll pan and weld a piece of metal over the holes and start over again. This time I want to cut two holes through the roll pan for the exhaust system instead on cutting out two holes like before which look like an inverted U. My question is if I run two exhaust pipes through the holes how much gap should I leave between the metal and pipes. I don't want heat up the paint on the roll pan. Should I use some sort of inserts and weld them to the pan for the exhaust pipe to run through? Any thoughts?:confused: :confused: :confused: :confused:

You could also wrap that section with header wrap.