The real issue is the slope of the grade. If you are forced into a steep grade, start and stop your grade very gently, say start with a half or 1 percent slope, then transition the grade as you go.
Take your longest engine and car and verify the train does not bottom out where the grade stops and starts. I use two Atlas 21" Budd cars. They are VERY unforgiving.
Avoid any grades that stop or start on a curve if you can.
