I actually use "spring" loaded turnbuckles on the front and rubber dampening ones on the rear. They are the ones that came with the Happi-Jak kit and the only items worth keeping. The bigger, longer ones go on the front and the shorter, stiffer ones go on the rear. I think that Bill is correct that the rear should not give much, if any. The idea is that the rear should act more like a hinge rather than allowing any chance of the camper to slide. The proper method to tighten them is to bring the turnbuckle in until all slack from the chain is removed. Then proceed to tighten the turnbuckle in by another 1/2" (this is per Happi-Jaks instructions and appears to work well). I then jolt the entire camper around by accelerating and slamming on the brakes a few times and then recheck the adjustment. I have found instances were the chains have slackened up.
I think that the Tork-lift tie-downs have changed somewhat. Mine were set-up so that I could adjust the angle downward away from the truck (adjust so that you have 1" clearance between the extension and the lip of the bed). I have heard that the new ones have lost this adjustment feature but come with a pre-determined angle (once the angle is set, there is no reason to adjust it).
UPDATE:
You can find your part numbers at Happi-Jaks (looks like I've never learned to spell it) web site:
http://www.happijac.com/AppProdGuide.htm#Turnbuck
And, yes, they seem to have their own version of the frame mounted tie-downs now. After all, they claim to have
led the way in tiedown technology for more than 28 years. I wonder how many truck beds they wrecked in doing so?
UPDATE 2:
John-
I'm not sure that you saw my other post, but I didn't realize that you have the Waag nerf bars. I wanted these as well, but I believe that they will interfere with the Tork-lifts (I believe that they will run into the bar). Something to consider before committing. Maybe we can swap some precision measurements. Waag was unable to answer this question.