... That's a good point. I looked at again and I think you're right. When it comes in I'll look at everything and see if I can get some nuts/washers on it. I'm not sure if there is enough room to get a hand and a wrench back there, but you never know.

 

What about a steel plate on the outside the size of the raised square portion of the tailgate where the factory carrier mounts? Wouldn't that distribute the weight a bit more? It would certainly be easier to do.

 

A thin plate would probably work quite well. Would you want to still use the factory nuts that are tac-welded on? Is there enough room to get your hand through the inside vent on the door to replace them with a nut and larger washers?