I would like to start by asking what size kettles you are using, because if it's less than 40 gallons you are going to be very unhappy with those burners. They can melt a pot.
Then again, you mentioned 8 inches, so they must be pretty big.
Okay... you don't want to powder coat the top rail area because the powder coat will burn off. We are trying an experiment with a stand right now: 2 - tone it's a powder frame and ceramic top.
I suggest you test before painting. Put a kettle on and fire up the burner and see just how hot the frame gets.