I am very interested in this too. I have a platform rack that I made for my 80 series Land Cruiser
that used the Thule rain gutter mount feet. I had myself, fiance, and my two girls (both under 6) up there for a picnic. The girls loved it and I was hoping to use the same feet and rack on the inbound JKUR. I know that Thule makes a bolt on artificial gutter that could be bolted thru the roof just above the rear window but what to do about the forward mount. My plan was to use the existing gutter above the rear door for the forward mount but they may have to change now. If that isn't going to hold 500 pounds or more, I may have to rethink my mounting plan.
here is a link to the Thule gutter
542 Artificial Raingutters - Thule