[freebeard]

I was thinking below the hitch, too. You're working between the lowered tailgate and the diffuser. This is what I've been thinking since I came back to the thread:

Two friction shocks at the pivot points. They need bronze bushings anyway, you could home-brew something or, from:
Friction disk shock absorber - Wikipedia, the free encyclopedia

Originally Posted by Wikipedia

Motorcycles of the same period, through to the 1950s, that used girder forks also used friction disk shock absorbers. These were often provided with a large handwheel, so that they could be adjusted easily during a ride, or even whilst in motion.