There use to be a product that you stuck to the side of the boat under the vent
opening while fueling. It would capture the spill. There is also a whistle
thing that you can put in the vent line at the tank. It is suppose to work by
whistling until fuel gets to it, I've never seen one but several people swear
by them.

Why is there a problem with routing the vent hose above the vent opening then
back down?

Mike