Absolutely incredible looking rig, your body panels look fantastic! Those rims and tires look fantastic too. I hope to hear how it runs with them, once you get it out on the trail.
I mounted my Desert Lizards upside down as well, and used two of the included spacers at the top of the rear shocks. I used the long medium spring under the plunger, and the soft spring on top of it, and I could not get the back axle to drop when I picked the rig up. I used both soft springs in the same configuration in the front, and it dropped just as I'd hoped. From my understanding, you want the rear to sit down firmer, when crawling, so you want stiffer springs back there, but those the stiffer medium springs might just be too much resistance. The other thing is the rear shocks looked like they were still at an inward angle, even with the spacers, so I bought a pack of spacers that I plan to experiment with as well. The shocks articulate smoothly, in both directions, I used some green slime on the o-rings, so I don't believe that is the issue, though it may well be that I need to use soft/soft in the rear as well. I haven't played with that yet, but it is on the list.
Great job so far on your truck, looks like it is going to be a monster rig!