Gordon
This is all up for discussion but your approach is sound. My feeling is that the train railway can run along the back of the whole display - there will be 16ft of lower level in front of a narrow raised railway - where it will be a backdrop.
The allocation of space at each end depends on the railway layout. What I would like to do is give you the freedom to come up with a layout that you are excited about. We can then work City Life theme sets into this.
Mark
I'm looking at a loop at each end with sidings inside it and, maybe, at one end a siding outside it being repaired. The internal sidings I'm planning to base on the layout I have in mind for my "permanent" layout which will be an end-to-end one. However, they will have to be reduced in size as the planned Beachtown terminus is 13 feet long and Seaport is 15 feet! But even scaled down, there should be room for Damo's station.
Damo, can you give me approx measurements, please?