Wow Matt,
My head hurts now! LOL
When I was teaching at Mount San Antonio College, I always felt I'd done my job if smoke started coming out of at least one student's ears. 
Mark:
Good choice going with flex. If you go from 8 pieces per circle to 16, you're talking about a huge circle, which is great for big equipment and long trains -- no so much for inside the house. 
A few years ago I was tinkering with a backyard design that was a minimum of 6-foot radius (O-144) with a 12-foot radius (O-288) in one section. Would have been awesome for really long trains and big engines. The wife took one look at that and said "Don't even think about it!". It may have had something to do with the staging yard occupying the [would-be] former location of her flower bed.
BTW, post a scan of the plan. Also, I stumbled across a potentially good material for ladder type outdoor roadbed -- PVC moulding from Lowes. I'm going to pick up a couple of samples to play around with as PVC is more thermally stable than HDPE synthetic lumber.
