I am lucky, the design of my boat
has the filler thru deck
fitting well below the vent, so the pump
nozzel shuts off well before any significant overflow occurs. Also the vent is on the side of the coaming with the deck
below it. Two thicknesses of paper towel is all that is ever needed to catch any little bit of foam that might come out the vent before it reaches the bay. Never spilled a drop in the water
(knock on wood!)
An additional benefit of this arrangement is that it puts the vent further away from any possible wave action. This is a diesel
tank. It would be a stupid (and illegal!) arrangement for gasoline.