I did the same thing. I made the table from plywood thinking that I would replace it with a stainless sheet once it was fitted correctly. After finishing the plywood it worked well and didn't rattle so I left it and it continues to be pretty handy on the trail. Just the right place to make a bunch of PB&J sandwiches.
That's basically what I've done except I have a small Yeti (different brand though) cooler that lives there. It was always a challenge figuring out what cooler would work best - hard, soft, whatever and where to stow it. The tailgate solution worked quite well.
That is very clever. I may have to make something similar for mine. Would be nice to have a spot to do some gunsmithing on the trail. I have an old MP40 that requires constant tinkering to keep it running. This could be the trail work bench I have been needing for years LOL