That's an interesting problem. Where are your fill and vent fittings on the tank in relationship to each other? If the tank is not level and the fill fitting is uphill a bit, I can see how that might cause a problem.
This is a 31, so tank is in the middle, both fittings on on SB side, within
inches of each other, the vent slightly lower. Anybody ever seen the
insides of fuel tanks PSC uses? All hoses are run to the top of the tank,
I assume fuel out is pipe to the bottom and the rest are not.