Even if the upper is offset? What about a parallel style four link?
As you can see I made the arms as long as I could. These are 48 inches from center of axle tube to the pivot, the actual arms are 43 3/8.
As expected there was significant plunge throughout the travel, but the driveshaft still rotatated freely and has some slip left but it is at its max that I am comfortable with. Even at full droop were still in the positive caster range which was a huge deal, it only gains and looses 8-10 degrees so at ride height I set it at 5-7 and bumped it gains to 10 and droop has 2-3 still. I am ok with that.
I am finding there is a lot of give and take with this.. It's amazing how big and small changes affect things. I still may attempt at 3 or 4 link to see what that does to the caster and pinion angles.