I have my adapter, a mesh top from Eric, and an OVMS (watching my son drive the car around SF). And I'm not a techy guy, so how did I get into all this?
So the secret to keeping the adapter from rolling around the truck is to put it in a camera lens case and lower it vertically between the seats. It will drop to the bottom, but you can pull it back up with the cord that closes the lens case. Keeping it there means you don't have to pop open the trunk to get it each time you want to charge--which I find nice on a trip with the trunk jammed so full that I don't want to open the trunk any more that I have to.