Hi Folks, thanks for the in-depth guidance here. planning to order the Prinsu this week. primary reason for the upgrade is my 21 cu ft yakima rocketbox does not fit on the stock lexus rack, sits too far back on the truck, the tailgate hits it when open. looks like a few of you have a yakima or thule box on top of your prinsu, any issues fastening the box to the crossbars?