I know its best to have the correct height to make the trailer level. But I dont have a boat yet and I also dont have the hitch part that goes into the 2" receiver box. Right now as it stands, the top edge of this box is only 11" from the ground. I know that I need some sort of step up adapter. What is a good height to start with for general purpose single axle stuff, like a 17' boat trailer or utility trailer? Is 19" or 20" about standard? Also, where do you take this measurement from, the top of the ball or the top of the tongue? Also, whats the most common ball size for that kind of stuff, 2"? Thanks.