[Brent Mills]

I'm not going to speak with any sort of super confidence, but I believe the return line is just and extension of the end of the fuel line...Instead of stopping at the end carb, it goes all the way back to your tank.

With regards to the fuel in the bowls, I remember someone saying that just before your ready to stop somewhere, flip off the fuel pump and run the bowls close to dry. I'm sure it'll take a little while to figure out when the optimal time to turn off the pump, but it should reduce the problem of fuel pushing into the cylinders...