There are six spacer posts. The one that Claw sees that is oddly uneven (and I agree with, thats one of the things that bothers me about it) is actually the wire loom that holds the wires for the brake light, and the hose for the washer nozzle. A couple other minor annoyances with the riser kit that I have are:
1) Perrin says you can't open the hatch all the way, they include stoppers to prevent full opening of the hatch so the wing doesn't hit the roof. It took a bit of adjusting, but I figured out a way to adjust the risers so that I have full hatch opening travel. My stoppers are now sitting in the Perrin box.
2) The washer nozzle now squirts on the ground, and will not even be usable at all if you're not stopped. Depending on how you angle the wing or add spacers, your nozzle will squirt the washer fluid on the ground. Not bad in the spring/summer as when I'm stopped at a light, I will just push the squirter button quick a few times, and most of it ends up on the window. If you're moving, you get nothing, as the wind now flowing underneath the wing takes the fluid away onto the car behind you (perfect if someone follows you too closely). I take the whole setup off in the winter.
If you can live with those, I personally love the mod as it gives the car a bit more of an aggressive look.
And since 09, isn't the WRX wing the same as the STI wing?