Rears up front arent easy, they are just cheap. I think I have about $20-30. I think it took me about 12 hours to build, and install my rears up front packs.
ALso, they ride awesome, flex great, and they are cheap. With a choice of all pro springs, or highsteer, I chose the highsteer (I was getting tired of cracking drag link seats)
All pro springs are a deal and a half for $50. Expecally if they are the older, non mexican ones.
As for the neg arch. My springs go into neg arch, when they compress the bumpstops.