You've got some things to consider with any seat. If you lower the rear of the seat with shorter springs and use short shocks you may angle the seat back too far and slide off the back. I knew someone with the lowering kit who had this problem and went back to the stock seat springs.
The seat hinge on the RE is unique. It is pretty tall and mounts near the middle of the seat, not the nose. If you want to keep the seat sprung you may want to get a different hinge that's lower and mounts to the nose.
You don't need to have the springs, you can mount the seat right to the frame as we've talked about before. This particular seat looks pretty thin but still appears to have good shape and padding, not just a sheet of leather over a metal base.
No matter what, you're going to have to get a little custom work done to get this mounted. What I'd recommend is getting a few 1x4s and 2x4s. Take them to the dealer, put the bike on the center stand, and stack them under your feet to see where your comfortable. Take the bike off the stand and see how much lower it is, take that much off the height of the stack. Than number is how much lower you need the seat.
Scott