Well I haul 2 50W's, 2 80W's, 4 Torsa 30's, 4 Trynos 30's, 2
kristal XL651's. I get some flex if I'm racing to the dock, but its minor. I have not put any backing on my UWS Toolbox. I think its due to the wide section width of each row, which covers most of the toolbox wall. On the other hand I do have a friend who had to attach vertical flat-bar on the inside of his less than well built toolbox. I know for a fact a friend of mine has a heavy duty Weathergaurd running 16 big rods of 4-80's, 4-50's, 6-30's and it works out well with no flex.