Loc: Red Oak, Galveston, and Pagosa...
My new, totally stock, Tundra 4x4 needed a 4 " drop. Trailer is 1/4" higher in front than the rear. Easiest way is to measure the trailer frame rail height from the ground and accommodate the difference between it and the receiver with an appropriate hitch.
On a side note, it is less critical on a single axle trailer, but a level trailer is still a good idea.
Loc: longview tx. usa
Take the trailer to a level parking lot. Chock the trailer wheels. Unhitch the trailer. Use a level to level the trailer frame. Measure to the toung. This is the correct height after the weight is on the truck