I used a clamp for a Tacoma with the side rail system. Drilled 1/2” hole in to the side Of the bed rail and inserted 350lb hollow walls. Now that I know it works I’ll probably install a unistrut side rail, secure it to the side with the hollow walls, and use strut nuts.
It’s secure.
GM told me sorry nothing out there yet. The tonneau mfgr. told me sorry and to return it. What I did works but lot of trial and error.
API Clamps (6 Pack) Silver... https://www.amazon.com/dp/B07K2L6FYP?ref=ppx_pop_mob_ap_share