What Mike says is so very true. A couple layouts back I wanted a ramp to an unloading spot for hoppers of sand and stone. I wanted to use an existing wood trestle I had, and only had a short distance to ramp up to it. The first time I went to spot a car there, I had a short string of boxcars with a hopper at the end. As I backed the cut up the ramp, the boxcar roofs hit each other at the point where the grade started! I had to use flatcars or gondolas as a handle to push the hoppers up the grade. It was pretty humorous.
Gary
Gary