Hi Phill,

I think AHPC sells an alu ring solution?

I ran away with your idea, straight down in the basement and made an alu-hoop. I was not going to say anything about it before it was finished and tested, but..
With some care and a blowtorch it was quite easy. Bending the tube without heating it was at best difficult. I did get some "bends" in the tube when shaping it, but nothing dramatic. Looks a bit rough, but with a bit more patience and skill, it will look just fine.

I used monel rivets to close the hoop, and have bonded some glass around the joint. Plan is to produce a fitting for the pole tonight, and glue the two parts together tomorrow.
Surface was prepared for bonding by grinding away all oxide with a rotating steel brush. This really roughened the surfece. Then used a drill-press to produce small pockets on the surface, to create a strong mechanical joint.

Now I am thinking about how to best attach the bag. Either by loops around the hoop, or a line threaded trough holes drilled in the hoop. Not sure yet..

Looking forward to hearing about your alu-ring experiments when you get the time.