Perhaps weigh the grill (with food for grilling) which will tell you the weight it places on the camper rail. I'd think you could exceed that weight slightly.
Such would prevent overloading the rail by not exceeding the designed rail load. And one could always add a single folding leg centered under the outside edge of the table too.
2012 Fun Finder XT 276 Toy Hauler & Harley Davidson Ultra Classic with Condor wheel chock
2014 Dodge Ram 2500 AT 4X4 Crew Cab 6.4 L Hemi, 373 gears, tow package, Rambox option, Revolver X2 tonneau cover, Equal-I-zer anti-sway hitch.