Digger:
Your points are well taken. The incident years ago was loading a Case 850 loader. I was real inexperienced back then, and had an uneasy feeling with the balance point equation, mainly because that loader had no brakes to speak of, and the drop was uncushioned. I was more worried about going over the front than anything else. I've since learned the equation of deck surface, muddy tires, front to rear and side slopes, rubrails, and the like.
In the more recent episode with the flat deck and beavertail, I was backing off. Truck was pointed a bit downhill, but more or less level. That JD 310SE, with the extendable hoe, 36 inch bucket and a thumb was really tail heavy. As I got to the ramps, the weight shift was sufficient to unload the tongue of the trailer, thus lightening the back of the dumptruck, which resulted in the truck sliding down the gravel road a bit. I had no where to go, so I hit the brakes and rode the slide out, some thirty feet before the truck noised into the bank. All I could do was watch the truck driver, who normally sits and rides the truck brakes in situations like this, sprint to his seat. He never made it. The other guy said I had a pretty comical look on my face during all this, but it took me a while before I saw the humor in all this. Lessons learned here - CHOCKBLOCKS!
All in all, think I'd still prefer the tiltbed, as I never seem to find a good loading site where the height of the braces on the ramps of a flat or beavertail trailer meet the ground as they should. All my jobs seem to be at the side of a gravel road, never in a flat lot. Guess life's always a compromise.