Right, to continue because the HW3 Rally demonstrated more deficiencies than just the farkle shelf.
I was deeply unhappy to have to rally without a top case. While it is true that most rally "stuff" is immediately available in the tank bag, that too was too small (something I knew in advance but I couldn't afford a replacement).
The main issue is that the subframe that carries the Aux. gas precludes the mounting of a case on the back, although it does strengthen the rear somewhat. Also, it's 'kludgy". It doesn't integrate well with the bike, but it did work well for the purpose. In addition, while the back rest I added worked well, it's fixed in place and I have a perfectly good Russell back rest that is fully adjustable.
So the design brief is to mount the Aux Gas while keeping the rear seat in place (for the backrest), integrate it into the bike and make it look good, all while costing nothing
Should be easy, right?
I tried a variety of mounting arrangements all using a combination of flat steel bar and clamping to a variety of places. None of them worked well until I came up with the following. In the pictures, the brackets are unpainted (for clarity) and not yet finished. More pics will come. The tank is a Summit 4 Gallon, and it has to sit far enough back to clear the backrest and far enough forward to allow the use of a top case. A Givi SR346 mount will come later to add strength, and I won't load the topcase until I have one.
Front brackets are located under the forward bolt-down for the grab handles:
They allow the removal of the side cases without interfering. The rear mounts are bolted to the rear mounts for the grab rails and emerge through slots cut in the tail piece. I hated doing this but it looks okay and will be unobtrusive when the mounts are painted flat black:
To prevent the rear brackets from slipping vertically, the mounting bar is a single piece running right through the bike:
It has to be this way, or it would have been impossible to feed through.
I have decided I don't like this because I will have to fabricate another piece to fashion the bend that carries the tank mounting pieces, so I have cut it in half at the center-line, and I'll brace it across the cut with a third piece.
Simple U-shaped "hoops" will be enough to carry the plate that holds the tank and cooler, maybe with a brace between front and rear hoops to add some stiffness.
More when all that is done.
Cost so far is about $20.