I've been thinking about this one for a very long time....how do I mount round external fuel bottles to the bike so I can carry a bit extra fuel? Where should I mount them? Is it even possible? I know for sure that I don't want them on my back if possible. The bottles are Primus 1.5L aluminum (3 1/2" x 12"). After months of thought on this, I determined the best possible location would be up on the front forks as high as possible, to avoid as much movement and vibration as possible. It then began to be a matter of how do I mate a tapered 2 1/2" fork tube to a 3 1/2" bottle? and not scratch my bike all up at the same time.
A trip to Autozone and the local hardware store and I had what I needed for about $30 - Floor mats to cut up and wrap, 4 hose claps, an aluminum door thresshold plate, a 3 1/2" drink holder, and some bungies.
See the picture above: