Scheme mark 2
It turns out that the scheme as described to below was more of a scheme.
I put the whole thing into an excellent, and now free, track planning program called XTrkCad. For someone (me) who expects every content creation program to have an Adobe interface, it was a but confusing, but the tutorials are very good and you can become fluent quite quickly. I was particularly impressed that it had all the components of the Peco code 55 track I'm using, and that it can generate easements automatically. It also allows you to run trains on the plan to check clearances and lengths of platforms, etc. Highly recommended.
You can see the results below, after passing them through Illustrator to block in the scenery, or download the PDF version as before. Unfortunately the DXF export from XTrkCad generates lots and lots of tiny curves which Illustrator doesn't anti-alias very well, so the track itself appears rather blocky.
Changes
The minimum radius is now 200mm, which is ample for the articulated tram stock used on the Enoden. I've also substituted the Kamakura High School station with Koshigoe station, at the suggestion of Doug Coster who pointed out that the platform at Koshigoe is rather shorter - only room for 3 coaches. He also provided some factual corrections for some of the background information elsewhere on this page. Cheers Doug!
I'm sorry to lose the school, but I think this makes more sense as it allows the interesting transition between private right-of-way and street running at Koshigoe to be modelled without running to another board.
I've also worked up an outline for a fourth board, attaching to the left side to create an asymmetric inverted U-shape, which would extend the JR line and add Enoshima Station. At the moment the left-hand side stops rather suddenly, and I think I may need a temporary fiddle yard to cap it off.
Concerns
The loop back under the upper level isn't on the plan at the moment. It should still work, but I'm not sure I can bring myself to do it since everywhere else the track follows the real thing quite closely.
The JR line at the back might add too much clutter to the whole scene, but it is an interesting thing to have there. I suppose it could be pushed onto the backdrop, but that wouldn't be as much fun. We'll see...
What next?
I can now cut the front frame for the final module now that I know where the water is going to be, so hopefully I'll have all three board frames complete today, and can get the jigsaw out to split up the plywood decks into different levels.