Here is what I did for the roadbed transition such as for industrial spurs and other short type of drops or inclines. As long as the grade is straight this works really well, trains WILL stay on the track. I used a chipboard type cardboard such as a cereal or shoebox. I first cut the cardboard into 1 inch strips, the longest about 12-14 inches. Stack the strips up to see how many you will need to reach the top and be flush with the cork. Cut the strips to length at 1" or 3/4" incriments. The first strip can be 1" the second 2" then 3" etc. Then glue them in place starting with the shortest piece first. Then the next to shortest, next and so on. The final strip will be the longest. This method will help eliminate the woop-tee-doos and make a smooth grade. At the tail end of the longest piece (after the glue dries) sand down the edge to remove the last little bump. This will make for a very smooth transition and minimal operational headache.
