Dang phone - my long reply disappeared.
Good points in the other thread.
Grade changes need a gentle lead in. Any time you can get some straight track at the bottom of a grade it helps.
Split the power feed for uphill and downhill sections. Use separate power supplies so you can manipulate the voltage. The old school solution is to use a rheostat. That way you just use one power supply but can reduce the voltage on the downhill run. Both methods work.