I mounted it as far forward as the side cover would allow when not using Smilin' Jack's aux gas idea.
In the next two pics you can see the mounting pads that are on the tube. But someone said they have broken on some (the tubes are meant to hold paper documents, not a full tool roll). So I used the tab + bolts into the tube itself. The large washers spread the load over a larger area. I used a long bolt (with full threads) to go from the out side all the way thru to the inside nut. So it had to be the same thread as the bolt holding the rear grab handle. Then I fitted the inside bracket to plug up into the slot available, already in the fender.
The rear mount is just a flat piece of 1/8" alum cut to size.
This pic shows both the flat alum piece to the fender (which I thought wouild do the job), and the added bracket where the helmet lock used to live. The front was complete and had no
in and out movement (flex). But the rear would still move right and left when grabbed by the lid and push-pulled sideways. It's been my experience that any movement like that will eventually break because of vibration fatigue. That little bracket 'cemented' the entire assembly together; there is no movement when grabbing and shaking the tube, the bike will fall over first.
This shows the front bracket pretty well, including the two bolts into the tube. There are fender washers on the inside, again to spread the load.
The lid shook loose on a couple of rides so I added the UV resistant bungy cord. This must have stopped the buzzing vibration because the lid hasn't come loose since.
The tube isn't aligned with the muffler angle; I didn't have much choice in the location, it just fit together as I worked.
For the curious, here are two pics of an idea I 'borrowed' from SmilinJack. It holds 1-1/4 gallons, and doesn't leak a drop.
In the beginning I rode carefully, not wanting to shake the two additions into fragments. However, over the last year, I've been riding as hard as I want, without thinking about the tube or the aux gas. This includes 100 mile rides down and back up Rampart Range Road, with lots of stutter bumps.
The guy across the street (ex-rider) asked about the aux gas and grabbed the tank, checking the 'secure-ness'. "Damn, that's tight." Yes, yes it is. The tool roll is a tight fit into the tube, it's fairly heavy.
If you ever see this bike, this clean again, call the police, it's been stolen.