Good reply. You're right, I hadn't thought about bridges / tunnels. Nor about the fact that the current system is basically "cheap off the shelf stuff". This e

Good reply. You're right, I hadn't thought about bridges / tunnels. Nor about the fact that the current system is basically "cheap off the shelf stuff". This exchange has been a revelation in systems-design for me. The value one gets from adding another brain with a differing viewpoint.