I just ordered my parts to put a seperate vent line on each bag. I am going to tap into the existing drain lines for each bag with a Y fitting and one way check valve right near the exit hole of the boat. It looks pretty simple and will also be nice to help water spill out when the bag is full and not get pushed through the aerator pump which is how it is currently set up. I would bet I loose 15-25% of the front bag capacity right now with air build up in the bag. Luckly, my bags have en extra capped off port right now I can screw a quick disconnect into and use for the vent line.

Total cost for 3 Y fittings, 3 one way check valves, 15 ft of 3/4" no kink line, hose clamps, etc... $35/per bag. It will be nice to have it filling the correct way, its just a bummer Supra did not look at this when they engineered the system. Guess I wont go into how disappointed I was with there fill system, although I just got finished upgrading that and it works great.