fuel tends to get sucked out in flight, and makes a heck of a mess / stains on the airframe
That's never been a problem. My vents are a short piece of brass tubing. I cut a 45 degree bevel on the end, facing forward. That way there is always a positive pressure on the vent whenever the plane is moving forward. It also puts a slight positive pressure in the tank, making life easier on the pump.
Joe