I ran a larger vent line from the 1/8" NPT fitting and added a roll-over vent valve which will close off the vent if inverted. This valve is located as high as possible under the fender well.
I also put a rubber ball under the flip top filler and safety wire it closed for track events.

I saw several cars with open vents and/or vented caps which spewed fuel all over when running on track. I've had none of these problems with my setup.