You have stumble across
Gary Hyper's Skunk Werx tank...
I think that is my pic too Dammit!
Gary tapped into his stock tank with a proper fitting, and added his own fuel cell. You can try to PM him, but he does not regularly read the boards... he is usually riding ALL THE TIME! I forget how much additional fuel he can fit in there, but he said that so far he had no problems. I believe there is a valve on the line leading to the main tank, so it is not always on and he had a quick connect as well... Hope I am recalling this correctly.
Gary just recently had a slight spill...
here is the link to that thread.
Another pic of Gary and Roy's Hypers...