Lewis, assuming you're trying to do something like this, you can't. The Lionel graduated trestle set for O and O-27 track rises 4 3/4" with a grade of 4.7% because you need that much clearance beneath any track for trains to pass under them. And that assumes that none of your equipment is taller and are able to handle that much grade. Other trestle sets rise even higher. Even if you make your own, you still need the height.
The 2nd photo uses 5" and shows you can get a 4.5% grade for part of the layout, but it's 9% for the other part, way too much of a climb and track under the others really needs to be 0" making the grade even greater.
Your dimensions are a bit weird, so I tried to figure them out as best I could to clean up the baseboard. I don't know if you drew the baseboard to fit the design or if there are limitations to the space. The numbers are the coordinates for use with the Toolbox dialog.
EDIT: I just looked at the rest of the thread and saw the photos of the decking, so you need to let us know the dimensions so we can see if there is some other way of getting close to what you are looking for.
At any rate, you can see how I use colors to identify different sections of tracks. The grades are purple, so I can quickly select them and change the end points for the the grade. In this case, all started out as 0", so all I had to do was change the high end to 5" and it displayed the grades. The key to this though is that all the tracks in the selected section need to be joined as one continuous section or you end up with the roller coaster. You can see that when I cleaned up the joints, some of the tracks got close to the edges.
