[Beastmaster]

Not having access to an SUT (except at the dealer), I hit the GM Media Website - the password restricted area.

I downloaded pictures that specifically hit the tailgate area with the midgate open and closed. I was able to get the full sized ones. You can zoom in quite well.

I've put them on the AZHOG site. You can see them at:
24.248.84.138/hummers/sut
or
24.248.84.139/hummers/sut

There's a couple of things that are fascinating. One is the series of rails on both sides. A good shot of them is pic X05HM_SU026.jpg.

What it looks like it's going to likely be is a 3 piece setup for starters/prototyping.

You've got these plastic pieces that need to be changed.

1) The horizontal piece that center mounted stop light is placed on.
2) The plastic facia under the lights and before the rail piece

What I'd envision would be:
a) Remove the plastic CHMSL (Center High Mounted Stop Light) foundation.
b) Remove the two side pieces between the C Pillar and the rear tracks.
c) Replace the side pieces with what we call (in the slantback world) the sponsons. Those are the triangular pieces. Those would replace the plastic behind the C Pillar and go OVER the fenders (for waterproofing). You then use the existing tracks as mounting points. (If you redo the contrast of this picture, you'll see that the fabricators did the same thing - use the track as a mounting point. X04CC_HM047.jpg)
d) Fit (with weatherproofing) a new horizontal bracket that accomodates both the door and the CHMSL.

The way the shell looks from the GM Media site on the H2H Slantback is similar to my musings.

If you take the two pics I've mentioned above, and put them side by side in some sort of photo viewer, enhance the slantback photo to show detail of the inside, you'll see exactly what I'm talking about.

-Steve