I also cap the fill line rather than the vent line. However, I only run one clunk in the tank. I'm so used to running lines to the top for vent and the lower corner as the fuel pickup in my boat tanks that it seems natural to do the same for airplane plane tanks. I always align the stopper so the fill is at the bottom, carb in the middle, and vent on top.
Edit: had to fix the tank color, I run Omega, not Cool Power.
