If my memory serves, in the champion 3000 watt, 1000+ page there is an extended run using a 12 volt fuel pump with a pressure regular but I believe it was directly connected to the carb not to the tank.
The whole issue of the honda's having a vacuum operated fuel pump is why you can draw fuel from an external tank but none of the other vendors (Yamaha, Champion, Kipor) have/had a fuel pump so a gravity feed was the only solution.
In addition to the gravity feed on a marine tank (which should work if it's slightly above - it will siphon the contents of the marine tank into your primary generator tank - you need to be careful how high above the other tank you mount it. As you increase the height it will increase the pressure in the tank and ultimately into the carb.
You need to check and see if your cap is vented or not. If it's got a vent then at some point the extended run tank will exceed the volume of the primary and leak out and possibly cause a fire.
I've been to the this movie myself and saw the ending. It's one of the reasons I moved from a Yamaha to a Honda because of the pump.
Oh, one more thing. You can purchase the honda vacuum pump (it's made by Mikuni) and run it off your Champion directly and create your own fuel pump to move the contents of the external tank into the primary.
