I have my tanks connected with 1/2" hose cause my tank selector valve switches the supply lines just fine but has the return stuck on the front tank, now when the front tank fills up to the top it just starts overflowing in the rear - if I start off with an empty tank it does look like my truck is getting real bad fuel economy, while all it does is pumping fuel front the rear to the front tank. Another nice thing about the transfer/overflow hose is that if I wanna fill up quick all I gotta do is open both tanks, also for reasons unknown to me the rear tank filler actually does accommodate the big truck pump nozzle, front one don't tho.