I just had a single solid extension bar. I think it's still in my garage somewhere. Even though my horse trailer was rated at 5,000# GVW, I used all 10,000# components. I used a standard Reese receiver on the truck. I checked the bolts frequently and retorqued them every year. I had to replace a couple of bolts, but that truck saw use for everything from hay fields to interstates. DO NOT weld the hitch to the frame of your truck as the frame has to flex and welds don't give at all.
