Well done on the research. Most miss these numbers. if you have the large pioneer rack the off-road ratings drops to 126lbs.
I see 200lb tents strapped to these backbone systems in videos all the time.
I made a couple of detailed videos showing the install process for the stealth platform and camp kitchen with icebox/dual drawer set up. I also had a top plate added with aluminum extrusions for extra storage capacity. I was tempted to install a shelf back there but takes it's place.