No experience with this, but a couple of thoughts while you're waiting. First, I think it looks OK--and I think plenty of aux tanks look butt-ugly. The only one I think looks both good and seems really useful beyond the fuel-holding feature is the one Dean Tanji made, and those are way rare. This one doesn't have that great extra cargo tie-down capacity his does, but seems good and functional. For the mounting part, it simply sits on your back seat, right? (Obviously it's secured there--I just mean it is secured on top of the seat.)
If so, and you obviously won't have a passenger, here's a suggestion. I take long camping trips and have a fairly huge waterproof duffel I tie on the back seat with a couple Rok Straps. It holds big bulky camping gear and the straps could barely reach around it fully extended. I didn't much like having all that bulk and weight up so high behind me, so I looked for a used stock back seat here on the forum. Removed the cover and cut away most of the foam with a serrated knife--I re-shaped it into a deep saddle shape. It now holds my big duffel lower and gives it a cradle for extra security. Much less hassle buckling the straps around it too. I bet that would work on the barrel-shaped Tour Tank. Of course, the stock seat goes back on the rest of the time.
Post pics if you get the tank.
