Hi. Thanks for the thoughts guys. I am building a railway that runs round my full loft, so it is 20' by 12', and on boards of 2' depth. I can't put a diagram up at present, as I haven't got one! I am building it in conjunction with my dad, and he is the design genius! What I have is 2 outside loop lines, that will raise 2" over 10 feet on one side, and 9" on the other (so 1 in 50 and 1 in 45 nominal). The thing is, under the lifted section will be a tunnel section with storage roads, so that will drop 2" from the same point. The two levels will have a gap between them of 4".
In order to build this, I am using MDF as a base board. The slopes will be on straights, so I shouldn't have too much to worry about. I am only looking at running 4 coach trains, or so, so traction is not a huge issue. I have set a test board up, and checked loads at 1 in 40, and it was ok for me.
Oh, and Brian, all this is happening no more than three miles from you!!!!