How to determine drop or rise
After you know how much weight you will be towing and the size of your receiver tube, you will need to determine the drop or rise necessary for your trailer.
Drop or rise is the amount of height difference between the trailer and your tow vehicle, whether that difference is positive (rise) or negative (drop).
The diagram offers a quick explanation for how to determine your needed drop or rise. Take the distance from the ground to the top of the inside of your receiver tube opening (A), and subtract it from the distance from the ground to the bottom of the trailer coupler (B).
B minus A equals C, the drop or rise.