#3) 6061 material was chosen because it is has a harder Brinell rating than 5052, but is softer, yet cheaper than the 7075 I original wanted to go with. It was a stronger but more price suitable material. Happy medium, if you will.... plus is much more scratch resistant than a softer grade. If you guys use your rig like I do. I want a surface that will stand the test of time from rugged use.
#4) Why 1/4" vs 3/16"... I can take a piece of 3/16" x 10" x 3' long and it deflects quite a bit when I twist it by hand. The longer the piece the easier to twist of course. The same size 1/4" piece still deflects, but it is about a quarter of the range. Overall just a much stronger piece of material. I've loaded one of my dual doors up with over 300#s with no issues.
I have had a solid 1/4 inch thick 6061 panel on my 80 tailgate for almost 14 years. I'd select that material again in a heartbeat. I left it natural and it has aged gracefully. Much more so than I have......
