Walt,
My recommendation is that you use basswood strip to elevate the 0-27 unloading track and straight track on both sides of the unloading magnet center probably around 2 feet for a relatively smooth transition. I have the unload/uncouple track for O gauge, you will have to determine the required shim thickness to elevate the unload and adjacent track to lift the car and unloading mechanism to clear the metal unloading deck platform. Your unloading platform base should lie directly on your deck, the shim strip should be in three pieces, one piece will be positioned between the bottom of the unloading track and the top of the metal base of the unloading track. The other two pieces should be equally spaced on both sides the 0-27 track that connect to the unload track to elevate the track. This shimming should resolve the interference problem.
