I want to add another sac to the port side under the seats to improve the surf wave. I have a 750 in the rear locker and I really don't want to add any more pumps. I have the rival system, so the rear bag has a fill line, overflow and then the pumpout line. My question is could I put a T connector on the fill line with a manual valve and then when the rear sac is full, open the valve and fill the sac under the seats? Then connect a line from the sac under the seats back to the pumpout line of the sac in the rear locker to drain? I hope I didn't totally confuse everyone