Saw a few planes with a mount to carry a rifle case based on a jury strut type clamp system. Who is selling them? Will it only work with a specific case?
No joy finding them on either airframes or the fadodge websites.
Parachute cord. Cheap, easy, very effective. With a -12 just shove it in back. You don't have to act like the -18's lack of space is something to emulate.