Here's an option on barrel mounting:
Grippy & non scratch.
Below it's shown held in place with straps, but will be best with cable ties.
(It's actually being worked on for mounting a camera to something a bit different to the norm)
Parts are:
Bicycle inner tube
Zip ties or straps
Camera hot shoe mount
http://www.ebay.co.uk/itm/Pro-1-4-Inch-Dual-Nuts-Tripod-Mount-Screw-to-Flash-Camera-Hot-Shoe-Adapter-/290957021302?pt=LH_DefaultDomain_3&hash=item43be63d076
Cut the inner tube, spike a hole in it
Dismantle the mount, put it inside the inner tube and poke out of the hole
Reassemble the mount
Wrap the inner tube around the barrel, secure with cable ties
Screw down a nut on the mount to doubly secure the mount
Screw up a nut on the mount to secure the camera