I am also building an RCR with dual fuel tanks/cells, and am looking for a simple way to feed from both tanks. The mechanical 6 port transfer valve looks clunky and the electric Polak valve also looks out of place and overly complicated. It seems that a lot of modern cars with dual tanks (new corvette) or with hump tanks (BMW, Mazda) are running venturi jet pumps in the secondary tank. The jet pump feeds the primary tank. The primary tank feeds the surge tank with a lift pump. The surge tank with integrated pump and regulator feeds the fuel rail. Has anyone tried using a jet pump in the secondary tank? The downside of a jet pump is they eat up the main pumps volume and pressure rating.