I was able to truly test my suspension last weekend with a heavy load and some moderate off roading. Hopefully this will help those who are trying to decide on perch height and rear springs.
Without any load, my truck maintained stock rake after I got the lift installed (though it might have settled some since then--I'll take measurements and post). I definitely prefer some forward rake because if your truck is level without a load, you will definitely have reverse rake when loaded. Once I loaded about 450# of water, food, and gear in the truck, the rear did sag a bit on the Bilstein springs. Here are a couple of pics of the truck with all that gear and pretty much a full tank of fuel:
450# isn't even that big of a load compared to some loads I have carried on longer trips, so I am beginning to think I should have gone with dual rate springs. And keep in mind that I removed the third-row seats and packed the heavier items, such as water jugs and coolers, forward of the rear axles to help distribute the load better.
The suspension handled the rough roads of Big Bend really well. I did hit some dips at fairly high speed that caused the rear suspension to hit the bump stops a couple times, but I was pushing it pretty hard at that point. Otherwise, I was really impressed how it fared on rough roads.
One thing I noticed was the increased articulation the springs give you. I don't ever remember my truck having this much articulation at this same spot in years past:
So, my impression so far is that this suspension system is great if you don't plan to load down your truck too much. If you do, consider some heavier rear springs. I'm still really happy with it.