Bunky,Your right I just notched the 2X4's so they fit tight over the divider. The notch in the dividers is 1 1/2" so it makes for a tight fit and the 2X4's just sets on the bed floor. I purchased a couple of quick clamps and made two braces for supports. You just have to remember not to hit the bed tilt switchNice idea to save the bed.
On a side note, how did you anchor the canoe rack to the bed? Did you use a 2x4 and then cut it (notch) and secure to the divider in the bed?