One of my friends bought one of these kits on ebay. The rear part of the kit was junk. However, the front part was pretty good. I just copied his. I made one for me and one for his dad. I made them from 2" square tubing, with 1/4" wall. And yeah, I just increased the rear preload to raise it. I can't remember, but I think I have 12" of clearance in the center.
This also allowed me to set the preload on the front softer, remove the anti-sway bar, and it rides pretty smooth.
I have the print for the lift at work. If you want, I can scan it tomorrow. It's not complex at all.
2008 700, totally stock with a few things added here and there.