It really doesn't take a lot to pull a cemented post out of the ground providing the bottom of the hole was not belled to a larger diameter than the hole itself. Once the initial suction and friction has been overpowered you are only lifting weight. Raising the bed about half the way then using the top of the tailgate allowing the weight of the bed to come back down using only gravity that is one way. Connecting off the side of the bead near the front will obviously allow for more travel, it's not likely there would be much more stress if any, on any part of the truck as raising a load that was loaded higher to one side than the other would do.