viatierra said:
You used the rails! I hadn't thought about that... Since the brackets hang down, does the jack bounce around? As for the other brackets, I'm not sure I want to be the guinea pig to mount those on the composite bed wall. I'd hate to see it crack or split. I wonder if fender washers would be enough to do the trick??
Since I tightened up all the bolts and put one of those handle keepers on it, it's remained quiet for normal driving conditions. I used fender washers in the rail (3/8" maybe? can't recall) to help distribute the load, and I think the 2 mounts are pretty strong. But if you didn't trust the rails, I guess a 3rd mount could be used.
For the bed itself, you could use bigger fender washers, or even a larger steel plate. The extra D rings I installed into the bed came with a steel backing plate, and I've used that many times to secure my trail bike (250 lbs). I can't recall exactly what size it was, but I'd guesstimate 3 or 4 inches square.