Freelance 2014-2

[faraway]

....., then use a sharp blade to trace along the distinct lines....
Wayne

That is the step where the curve gets messed up. The only method that works for me "sometimes" is to use very thin styrene and cut it with a scissor along the line made with the pencil following the rail.But it requires to use styrene as thin as paper to get the pencil line like described for paper. This is an old photo using that technique.
The blue foam ends at the ties and the very thin styrene extends up to the side of the rails. Between the rails is blue foam only. It is flexible and follows the curve.