Not too impressed by your latest suggestions, David. And you forgot chewing gum.
Hose clamps seemed a bit marginal too, if nothing else due to lack of bearing area, not sure if they would really be strong enough either.
The shaft collars would work well I'm sure. But - the steel ones are kinda heavy. And the aluminum ones kinda expensive - then I got to thinking - what's strong, light and cheap and clamps around a tube? Aha...
I can't see that a properly tightened muffler clamp could be head-butted via a polyester strap into sliding along a roll bar tube, they should be easily able to develop a ton or better clamp force...??? And the saddle part should offer good bearing area.
Al Seim
HP VW Scirocco