I am about to start the next phase of my layout, it is about 3 inches taller than my existing board. I know the grade limit is 4% with the 2% grade being preferential (HO) . I have seen some whalter risers but they are all either 1inch or 2 inches . Are we suppose to trim them to size to fit the grade? If I do this by hand with wedges of wood do I need to top the risers with 1/4 inch ply or something else for a base for the track ? Just looking for some direction on my "ramp up to the other 2/3 of my layout.