Exactly, Ultralite. The second skin was mentioned in that white roof paint topic months ago, it was probably you? I'm also messing with ideas for roof mounted or roof-stored solar panels. Have a deck makes a lot of things possible and easily configured or attached.
Both ideas were in large part about shading the roof. I used to spend a lot of time in SoCal deserts, hope to do so again. So 'shade' is high up on the list. Partly why I'm pushing thru to finish my awning project too.
I'm looking at bar straps, EMT, or 3/4" square tubing for cross braces right now. The straps would be no-weld, I can bend their ends to form hangars, have already figured to use 5/16"x1" carriage bolts as my attachments to the side rails, as the square shoulder of the bolt perfectly fits the inner slot in the C-extrusion side rails of the Z-71 rack. And the carriage head sits well on the interior lip, no extra bracketing needed. Put it in the rail, a fender washer, the bar metal or whatever attachment tab of the cross bars, a star washer and a nylock nut. With (4) crossbraces and the plywood providing most of the structure, it should be more than enough for my purposes. You'd probably want 4-5-6 braces of 3/4 tubing or 1" square if you intend to use it for a viewing platform.
I'm also looking at the front fairings of the Z-71 rack, looking to integrate a light bar mount into the rear screw position on those nose fairings, so the light bar sits trailing but above my sunroof yet still below the top of the rack railing. Probably make a tilt-down guard / glare shield for the light bar. And that way light bar is separate from my deck, in case I ever really need to break it down. And the light bar is protected somewhat by the rack itself. I could fab a more robust mount that is itself some sort of protected housing. 3/8" rod making a sort of cage, maybe. But I like the idea of a sheet or plate metal front fairing on the light bar, painted satin black like the rack, that just tips down to unmask the lights and serve as a glare shield. I'm trying to sort of conceal all the stuff I'm adding to the vehicle. Or at least make it non-obvious to the casual or idle observer.
I'm also thinking to run m electrical up the interior C pillar and into one of the middle feet of the side rail and up into the rails. I want a all-weather power-port-style connector up there for solar panel connection and for some moveable / clamping area lights. And I'm thinking about the rear / backup floods inset in the rear rack fairings. I want it set up so all three 'systems' work together but also work without each other, so I can easily reconfigure things whenever and however I want. I have a bunch of other power related plans it is all tying into.