Simple sleaves?

Roy Hughes

If a smaller diameter (22mm?) carbon fibre tube is rigid enough then you could try a split sleave of thin 1 inch diameter alluminium tube over it for the grub screw to bite into.  This would spread the load on the carbon composite. I note (on ebay) that the clamps sold for carbon fibre tubes are not dissimilar to (posh) pipe clamps, so it might work.