Naio wrote:
Any type of string, nylon strap, etc., that goes from outside to inside is going to wick water in when there's rain, and get your seat or floor wet....
I have done this looping a common 1" cam strap through the door window frames and do not remember any water issues. For clothes hanging, thread the nylon strap through a length of rigid conduit. The problem here is you need to undo the strap to open a rear door. You can also loop the strap over the cab and above the door frames but risk rubbing paint. If you do this, and get a vibration at speed, put a twist in the outside strap.
If this clothes bar is going to remain in place for the entire trip, you could build a "swingset" structure that had legs in the crease of the seat and legs to the floor of the truck behind the front seats.
Hope this helps,
