Kirk's fuel return dumps right into the baffles that he welded into the fuel tank. Theory is that the return fuel is hotter than the fuel in the tank, due to the baffle design it's not allowing the return fuel to mix with the rest of the fuel prior to circulating through the pump again, thus a constant cycle of heating up.15 gallons should be plenty for a day. I don't understand your fuel theory. Mine dumped right above the fuel pump. The fuel in the tank is plenty good as a heat sync.
If you are burning 15 gallons for a day of trail riding and having heat problems with your fuel, you have some other issue.