I have personally had the OLA tent (both of them) on my LR3. The large tent is very large, but two round Yakima bars (and pedestal feet) held it up fine. However, this was the prototype with a heavy plywood base. I'm not positive, but I think the production units are getting lighter weight components, I'm not sure if that means a composite base or what. Ask Buddy at OLA for details on that.
In my personal opinion, the larger tent is just too big for the LR3.
The smaller OLA tent fits the LR3 perfectly however. I had one mounted to my Hannibal roof rack, which is mounted with two Thule square bars, with myself and two kids (figure 425 pounds), it was absolutely stable. I suspect that the Hannibal rack helps dissipate the weight across the entire floor, instead of concentrated point loads on the load bars themselves.
In general, I think the Yakima round bars are stout and more beefy than the Thule square bars.