Nice work. One recommendation I have is that you put something between the slide and the tailgate or you will start bashing your tailgate.
When I built mine, I covered it in dark gray outdoor carpeting from lowe's. When I was done, I was trying to figure out how to make a latch to secure the shelf and keep from banging around. For me, an extra piece of plywood from the shelf roughly 1/2 inch thick double wrapped with carpet fit perfectly between the edge of the shelf and the tailgate. So with the tailgate up and the shelf in, I just slip it between the two and nothing is rattling around.
I may look at doing the double slide as well...
2001 Range Rover 4.6L SE (SD rack, ladder, Warn xd9000ce, steering guard, axle guard, diff guard, sliders, coils, 33in KM2s... no chrome)
2003 4Runner 4.7L V8 (wife's)
1985 E30S52 (1985 318i w/ 1998 M3 drivetrain, OBDI and 5-lug conversion)
Far better it is to dare mighty things...even though checkered by failure, than to rank with those timid spirits who neither enjoy nor suffer much because they live in the gray twilight that knows not victory nor defeat. - theodore roosevelt