I had about 20 pieces of 4x8 sheet of 3/4" plywood evenly stacked on a snowmobile trailer...zero tongue weight and pulled that from Oshkosh back to Appleton with a Jeep Wrangler in '85.
Almost didn't live to see '86.
At about 55 mph on Hwy 41, going over the Butte des Morts bridge, the Jeep, with 6 people (including me) in it, started oscillating...crap was starting to head for orifices that were tightening up like they'd never been tightened...first thing I did was take the foot off the gas and grab the wheel hard and hold the thing as straight as I could...when the oscillating quit...not one person said a word ... and once we got off the bridge (doing about 35 mph w/flashers going) we decided that the highway was WAY TOO FAST for where we were headed...we decided that the extra time needed to drive the lake road was time well spent...
Seeing the guard-rail up close and almost personal (the water/lake was also in the near vacinity) was enough to TEACH me to load trailers with more attention than I had given before that lesson.
That said, the lessons on camber, caster and toe-in/out is additional levels of knowledge that I would prefer not to personally test - but I do understand the physics of said items enough to know they make sense quite well. And not loading trailers properly just adds up to STUPID if any/all of the above items are not taken seriously...
Keep in mind...safety chains, ball-hasp locks and proper lighting are considered by some as window-dressing, but I won't touch a tow-job, trailer or vehicle if this stuff isn't 100% functional and safe...lighting alone, if not working, will run you over 150USD with the additional, obligitory, 3-points on your driving record in Wisconsin. Let's not even discuss what happens if the safety chains aren't attached properly or the ball-hasp is properly engaged.
That's for another post...pictures will be included...