Before you commit to that check out Manfrotto mounts. I have one and I sourced one for Pete Blackie - commecial quality, solid and beautiful quality. Large bracket clamps onto roll cage bar then has a universal swivel mount - unlimited postioning except for any restrictions imposed by cage bars. Solid as. Cost me about $240 sourced from camera store in Hamilton (Snapshot). It's not damped other than rubber facings to clamps, but you will have no shake issues as long as you camera has good OIS - my Panasonic is superb, and Canon should be good too (they invented OIS)
Cheers