just make sure if they are in your car to keep a blanket or something between them and anything else you might be carrying.
I had mine in the back of my pathfinder but the blanket i had around it somehow fell down and my bc wheel’s plates scratched up a bunch of paint on my KH 
In my experience, my unicycles get their most wear & tear during transit. Mostly being loaded in and out of vehicles, and also some during transit if they weren’t packed well.
I use a minivan, because it can fit several people and a lot of unicycles without anything being out in the weather. But they can slide around or fall down back there (I usually lean the wheels to one side, but sometimes they fall over). They don’t slide around in regular cars, but you have to watch out for pedal damage, and dirt or grease from the unicycles in the car. I used to drive with giraffes a lot, and they need special consideration to make sure the chains aren’t up against the upholstery.
Who cares if the paint gets a little scratched? If it really matters just wrap it in a blanket or something.
But i know it’s not a big deal, it’s just one of those things that’s annoying because it happened for stupid reasons as compared to me wrecking it on my own while actually using it, ya know?
yea lol, every single uni ive had gets pretty scratched up on the first day of use. and gradually worse as time goes on. but i like that look 
munis look better scratched up and dirty. 
There are two more unis in the trailer and we could put 5 more bikes on that rack. I’m pretty sure we could fit the Cokers on there too.
Hell yeah!
How about wrapping a sheet of foam rubber, loosely tied, around some of the cycle? Foam and a length of light cord is cheap. Should stop it sliding around and any knocking that does happen will be muted.
Some picnic rugs are backed with foam so perhaps wrapping it around with rubber side out will be a durable way of doing this and it would be so large that you would not even need to tie it on.