Tank vent problems

[67RS]

I have the full vaporworks setup, Rick's tank, ZL1 pump and pwm controller. I have the ridetech cap and filler neck and Brian Finch's overflow tank. The problem is that the overflow just fills up and pukes fuel anyway. I also filled the tank at the gas station for the first time yesterday and it would only fill for 1 or 2 seconds at a time before kicking off the pump. I know the cap isn't vented and I plugged the hole in the filler neck. The overflow is mounted in the trunk so it's higher than the tank. What am I missing? Is the -6 female port on the front of the tank not meant to be the vent? Do I need to add a second vent?