I am no pro, but hear are some suggestions you could try. Red on the sides would be vertical. The blue should work as well, but you would need to be careful loading and unloading stuff.
Hopefully the more experienced folks can offer you more ideas.
Yes, you can definitely do it, are you wanting a dual or triple (for better DE coverage) back there (also which brand Jammer)? I would suggest a similar placement to a pickup truck. like discussed here: https://www.rdforum.org/index.php?threads/84225/ you can mount them to the bumper in that gap between the bumper and the door