Thanks, would like to do something similar after I finish the first order of business w/the bike. Did you fab or have-done the aux. tank or is it avail from a jobber? I have thought about a swap-on below the rack w/the cargo space above, & perhaps some additional bracing for the rear of the rack to make it rock-solid for fuel loads & a reasonable rack load. I was thinking of a trapezoidal shape to follow the contours of the sissy bar & well-inside so that it wouldn't be at risk of rupturing in the event of an accident. Maybe something taller & longer front-to-back than wider... . Two to three extra gallons, by then I think my kidneys need a break!
So, did you tie-into the gas line by the fuel pump? Thanks about the ball-valve for the aux. tank.