I teach a course in “Reverse Engineering” to undergraduate mechanical engineering students at Johns Hopkins University in an effort to give them some engineering intuition and practical application of their theoretical learning. The course is affectionately referred to as the tractor class, because we disassemble, analyze and (sometimes) repair a Ford 8N tractor. One of the early lectures is explaining the 3pt hitch and the genius behind it in preventing the tractor from flipping. We then analyze the potential for rearward flipping dragging a plow at the draw bar. The exercise requires understanding engine horse hp, drawbar hp, weight of the tractor, etc. Much of the information to complete the exercise comes from your Tech Note 21. I have referenced this note for several years, as it has a wealth of information, is succinct and very well written. I wish all reference material were as well prepared as TN21. Thanks for you effort!