Fitter,
Are you planning on building this layout in a room dedicated to it or will it be in a multi-use room?
If it will be in it's own room, I would recommend NOT using a 4X8 but instead building shelves (anywhere from 12" to 30" wide) around the walls and leaving the center of the room for people. That way you can use larger radius curves, and you will have more room for your power plant, coal yard, oil refinery and town. The only drawback to an around the room layout would be doorways and how to deal with them, duck-unders, liftouts and or drop-leafs.
Check out you LHS for some of Kalmbachs layout books. Also pick their brains for some suggestions.
Dan Raitz