A full description of the aux fuel mounting and configuration follows the image gallery.
Here are more details.
I rode down to Chula Vista with Doug yesterday to meet up with Mike Langford. After some back-and-forth, the consensus between me and Mike was to mount the fuel cell on top of my existing Pelican case mounting plate.
The fuel cell is a 4.6 gallon from RCI. At 6.2 lbs per gallon of fuel, that's 29 pounds when full. and the tank itself is 9.6 pounds, so we're at less than 40 pounds total. The Pelican case mounting plate is a 12"x12"x0.15" aluminum plate, and attaches at four points to the stock rear grab rack on my FJR, which has a Garauld stiffy kit installed to support the rear sub-frame.
Mike fabbed up a set of 1" aluminum rails which bolt onto the Pelican plate. The RCI tank has four tabs about 1.5" in from the corners on the front and back sides, and these are bolted to the rails in the front. In the rear, the bolts extend through the rails, and lock nuts secure everything.
Mike installed a manual valve to initiate a transfer. The valve attaches to the tank and extends horizontally towards the rider's left side. 5/16" fuel line then passes between the front seat and the pillion seat -- my custom seat leaves a noticeable gap there, so there's no kinking. A quick disconnect sits in the tray right next to the CCS servo, with 5/16" line extending to the bung you installed on the bottom of the tank.
Using the existing Pelican plate as the mounting platform provides a lot of advantages. It lets me swap out the aux tank for the Pelican case with a minimum of fuss, lets me keep my seats installed, and keeps the stock rear rack and support members in place. All that works well in my mind.
Here are some potential downsides, which don't appear to be deal-breakers to me, but I'd appreciate your opinions. 1) While I regularly carry more than 40 pounds in my Pelican case, that's still a lot of weight on the stock rear rack, and the 12"wx12"dx8"h tank concentrates the weight in a relatively small area. 2) There's no way to run with both the Pelican case and the aux tank at the same time. 3) It's a little screwy to run the fuel line between the two seats. One alternative we came up with is to drill an opening at the lip of the blue plastic at the back of the pillion seat, and run the line back from the tank into the hole at that point, then route it up to the QD under the driver's seat.
Since the original install, I rode down to Hal's house for some new tires, an oil change, and his advice on the fuel cell. We wound up re-routing the fuel line back to a new hole drilled behind the pillion seat, which cleans things up a lot. We also replaced the clear vent line with some 5/16" fuel line.