The clearcoat is fuel proof to Nitro, Gas, Kero, just about anything you can throw at it, it's an automotive 2 part clear. I use the PPG concept line clears, 2021 and 2001 clears, I am trying the 2042 as well now. I have also used with PPG Omni MC260 quick clear with fantastic results and if weight is a dead strick issue, I prefer the Omni, it's a lighter clear in the end with less effort than the others.
For flat finishes I use the PPG 2060 flex'd n flat clear.