The last words of Part 1 were “Obviously I have to check these measurements with a mock-up before I start cutting things to the wrong size.”

And, yes, when making the mock-up I forgot to account for the 5mm between the rail edge and sleeper edge.

Here it is fixed:

So the main “slab” that will go between the back edge and the first sleeper edge should be 109x1185mm. It will have to be cut from five A4 2mm sheets. The leftovers will be used between the tracks, and on the “front bit”.

All well and good, except it isn’t. I’ve now found a better base board (from part of some unidentified furniture that my neighbour was chucking out that he asked me if I had a use for).

The board is now 800x230x38mm.

This will allow me to have that original 50mm to the rail edge, or 45mm to the sleeper base.

So now I need 124x800mm of 2mm card cutting and gluing down. So I can finally get some work done (only putting one track in for now, to gauge how it will pan out).