Another strategy for your consideration. No, it is not mine but an old timer let me in on the secret and it has been used every since. Empty truck and trailer, sit in the drivers seat. Pick your target, aim at it, and memorize. Your are only trying to level the vehicle. Start at the back of the trailer loading heavy items. When you are out of sight of leveling start loading the truck bed from the front to the back. When you are back level, start reloading the trailer from the axles to the front. When you are on target, stop. Drive like you do not have brakes and you will not have problems.
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