From the research that I did, the ones that came from the factory with the rack had more bracing. However, many dealers had port installed or installed on site racks, but they did not have the additional bracing.
I bought some 4runner racks from a 2nd and 3rd gen and I had plans to put them on the roof, but the thought of messing up a perfectly good roof scared me away. Additionally, I have always wanted a sunroof, so I talked to local install place that has a great reputation. He will install the 4runner rails while doing the sunroof install, and believes that the sunroof will only strengthen the roof since its just sheet metal at the moment. The power sunroof install will entail adding the bracing for the slider.
The reason I like this idea is that it will be done by a pro and it will allow me to use the defender mounts for stock vehicle roof rack rails with my Conn-Ferr rack.
This idea has been on the back burner due to lack of funds, but I am very close to pulling the trigger and just doing it.