Bed cover with Yakima rack - DIY?

I have a Yakima rack (for kayaks) and looking for a way to secure some things in the bed. Did a very brief google search and see some others doing it with plywood or other sheet goods. Back story is I am driving about 7 hours to buy an RV travel trailer and then camping near where I pick it up before driving it home. On future trips I could put stuff in the trailer but I could see a cover being useful from time to time later. The rack attaches to the side rails so I would need to cut out for those and it wouldn't be rain tight but I think that's ok - I could put stuff that water would be an issue in totes. Staying one night in a hotel on the way so need it reasonably secure so our stuff doesn't walk off. I have some 1/2" plywood left over from recent projects. Looks like I could just cut it to lay on the sidewalls with cutouts for the rack brackets and fasten to the side rails. Anyone done something similar? Does anyone make a cover that would work with the rack?

 

Something like this. I see a few things I would change for my own use but it gives the general idea.

https://www.tacomaworld.com/threads/diy-tonneau-cover.437207/