I agree with d pierce about the extra vent in the highest part of the tank. Maybe we could just poke a hole in the plastic large enough to get a greenlee hole punch in to make a clean hole (should be no shavings this way) and then install the fitting to the tank and run the vent hose up to the other vent and "tee" into it. You'd have to be able to reach into the tank to use the hole punch and install the fittings for the hose though.