I'm just knocking around ideas here...
The Rocket is of course fuel injected and it has a sealed unvented fuel tank with an electric fuel pump contained in tank. The fuel is under pressure as it is delivered to the injectors.
You could do one of two things possibly to add another tank. First would be to put a simple electric fuel pump in the remote tank and when you run low on fuel you would have to stop, pop open your gas cap, and manually run a hose (from your remote tank) and fill your primary tank from it, and then close the gas cap and put away the stuff from the remote tank. I don't like this idea but if you had to cover long distances between gas stations it would be better than nothing. It would be just as easy to carry a gas can.
You could buy a second Rocket fuel pump (with the fuel pressure regulator built into it) and install it into the remote tank. Here's where it gets a little tricky. Some pickup trucks had dual tanks (that were fuel injected... notably Fords) and they had a switch on the dash to switch between the two tanks. This switch turned on and off fuel pumps depending on which tank you wanted to use. I believe that the fuel pumps themselves used the fuel pressure regulators as check valves. If you didn't have some sort of check valve the fuel being pumped would attempt to refill the empty tank and drop fuel pressure. You need to turn off the fuel pump not being used because the fuel itself cools the pump and keeps it from burning out. A setup like this would allow you to switch tanks on the move. You would want fuel gauges for both tanks I would think. The remote tank should be made of something that is hard to rupture in an accident, and won't spark or conduct electricity. If done incorrectly it could be a fire waiting to happen.
I like to stop every couple of hours or so anyway
so this setup probably isn't for me, my rides are controlled by Monkey butt to a large degree.