Yeah, shock absorption would be a good thing. I had a RAM mount on my dirt bike. The shock absorption was limited to a rubber coated ball that the holder attached to. I had to wrap electrical tape around the batteries to keep them from rattling and building up carbon on the ends . . . . until I hardwired it to the bike. It's all bike stuff . . . . but maybe you can get some ideas here:
http://www.cycoactive.com/default.htm I found this site too:
http://www.gpscity.com/toyota/all-mo...hbyvehicle.htm