Stewart,
This all depends on the layout and which trains I expect to run. Knowing I have very limited space for our formal living room Christmas layout eliminates the running of the big Williams UP that only runs thru 072 switches. Also on the Christmas layouts I run notoriously slow so everyone can see everything, so when building this kind of a layout, I build right up to the edge of the platform. With the bigger layouts I am much like Brian and leave about 2-2 1/2" of platform as a turning bumper. As I go up however the 2nd, 3rd and 4th levels, usually get farther and farther away from the edge of the platform. When I get up to the 5th level, that I use for my bumper street cars, these trestle actually come clear out to the edge of the platform for ease of changing the bumper cars wen desired. The higher your levels go the more slow speed running becomes important, especially with big expensive engines and rolling stock. DCS & Legacy make this an easy control situation.
In the 1st picture the programming/bumper car track, actually extends out over the power tables as part of the 2nd level, for ease of programming all DCS engines.
PCRR/Dave
Notice in the 2nd picture, the Height of the Tweety & Silvester Bumper car, and how close to the edge of the platform, it really happens to be.
