This is the "slim trunkrest' from Corbin.
http://corbin.com/accessories/502.shtmlI ride 1-up, without the tourpak, about 75% of the time, and I like the more streamlined look when I am riding with the pak on. They give you the little pad beneath, on the lower front face of the tourpak, but when they make it, it has velcro to stick it on. I didn't want the adhesive on there, so I unstitched it, added a rigid plastic backing inside, and sent some screws through. Now it bolts on through the existing holes in the TP, no adhesive required.
While I had it apart, I filled it with a piece of 2" memory foam, (5 bucks, a remnant from the bed store). The stuff is cool - I had to flatten it like a pancake to get it in there, but then it expanded to fill the leather pouch, so the pad is about 1 1/2 inches thick, and molds itself right to my gal's tailbone.