I am sorry..I didn't notice that the panels are bolted to the top rack. That changes everything as far as weight carrying capacity. Nice!
No need to apologize.
You are completely right about the suction cups for phones, tablets, etc. They don't always hold like they should, especially in NC humidity, lol.
The suction cups are only there for stability at the bottom, and greatly help with installation.
The panels are mounted with 4 bolts to a second panel section that then mounts with the supplied grade 8 hardware that comes with the roof rails for the roof rack - or they also supply 4 more bolts, washers, and nuts with the panel in case you don't have rails in that section.
It's very sturdy.
I weigh around 270 at 6'5 and I can't make it move at all once mounted.
I attached a few more photos of everything laid out to give you, and others, a better look at what all comes with it.