Turnbuckle advice

I'll say the same thing here that I posted in reply to your question in the FB group:
Spring loaded are a must.
If it were me, I'd sell the Happijacs and get Torklift Fastguns for all 4 corners

Torklift parts might be expensive but they are well engineered and built to last.

Torklift makes at least three price ranges of turnbuckle that all carry lifetime warranties. Happijac also makes a spring loaded turnbuckle. The two more expensive offerings from Torklift make setting tension easy and consistent while the offerings require more work when loading and unloading your camper but still will safely do the job.

No alternatives from my side. I have been a happy TL Fastgun user since 2009 and recommend them.

Thx guys. The Torklift springs seem a little pricey for what they are. Any alternatives?

The earlier bumper rear mount depended on the flex of the bumper to act as a spring . If your rear mount is frame mounted it should have a spring .

All 4 “should have” some sort of spring in them. Weather frame mount bumper mount or bed mount tie down locations.
Anything from a chain and hardware store turnbuckle or a 2” ratchet straps will get you home, but with no relief in the tiedowns you risk bending something or ripping a camper mount off when you hit a large bump or twist the truck frame much.
That said just cheapo turnbuckles and chain work fine but need a spring. Either in the tie down or on the truck side mounts like the little ones torklift sells.