I wonder if that is a bad thing, though. In some of my old posts, I muse about converting the rear to leafs while 3-ilnking the front. The idea being that the 80 is too heavy to be an unrestricted slinky, so you really need one end with some resistance as articulation increases. People thought I was crazy, but take a look at some 3-link XJ's retaining the rear leafs (they are also a ton - literally - lighter than an 80).
It's interesting to see the rear on your rig providing some resistance now, which makes sense given a 3-link is totally unbound. But looking at your pic, the body is staying very level while the suspension works, and dropping that driver's rear down as you come off the rock on an unrestricted rear suspension setup...would it get floppy?
If I was on that line, my front end would be flexed, but still pulling the body down and the driver's rear would be max stuffed. Your suspension is handling that better, meaning I'd get tippy well before you would as it would want to come off at a lean whereas the more stable rear on your 80 holds the body while the front does the extra work.
I don't know - it's almost impossible to tell until you do it, but I'd be really wary of losing one end keeping the body level while the other does more work with this much sprung weight.