I am too paranoid to use magnetic or suction mounts. I need to have mechanical attachment - u-bolt the sucker onto a luggage rack, something like that. I used to have a car set up this way, with a piece of PVC pipe, cap glued to one end and screw-in cap to the other. I cut a slot in the back end so I could slip a rod with a reel into it, in a pinch. I didn't have expensive equipment in those days, so joggling the rig around while traveling didn't bother me. I wouldn't put my Hardy Zenith into a PVC tube, though.
Longer transport, I just break the rods down and re-tube them. Well worth the extra few minutes to re-rig a rod, AMHIK.