Roof rack capacity of the Jimmy?

I bought a luggage carrier, secondhand, with the intention of using it for extra storage when we go camping. It is large enough that it will have to be mounted directly to the crossbars on the factory luggage rack.

The paperwork with the carrier says the rack must have a minimum capacity of 100 lbs., with 150 preferable. I would expect to carry at least that much, anyway.

I'm waiting for an answer from the manufacturer (Thule/karrite) about ordering the u-bolt kit to mount it on the bars. Seems they sell the damned thing without it.

Does anyone know if the GMC factory luggage rack is strong enough?

200lbs evenly distributed.

Thanks.