RCR Fuel Tank/Sponson Venting

Just getting ready to close up the fuel tanks and it occurs to me that there is plenty of opportunity for fuel vapor to build up in the sponsons -- not a comforting thought.

What approaches have you guys taken to venting the sponsons? I have ended up with a few additional drill holes at the bottom from various attempts at locating tank-hold down hardware but that just serves to vent any fumes into the rocker panels. To my my mind, any effective venting needs to:

1. Have two openings -- an inlet and an exhaust
2. Have a continuous source of fresh airflow to scavenge the vapors.

With that in mind, the only effective sponson venting I can think of consists of openings in the front of the sponson (extra holes drilled in the cover plate behind the front wheel well) and matching holes at the rear of the sponson. Forward motion of the car forces fresh air continuously through the sponson, evacuating any residual fuel vapor.

This arrangement introduces the possibility of water/mud/moisture entering the sponsons however.

Is fuel vapor build-up an issue and, if so, what are some solutions people have tried?