Hi Michael,

It would be desirable IMHO to have a means for defining the minimal curve on a surface (similar to rhino's geodesic spline). Also known as Plank Lines, (referencing timber boat hull construction) it is the shortest path between 2 points on a surface which if used to sweep a band over base surface results in a strip that is tangential to that surface over its full length that could be unrolled to a straight strip. This could simply be achieve with UnwrapCurve script of the original rail curve, since long edges are straight & parallel.

Below is an image of traditional hat fabricated from bamboo strips analogous to this technique.

No doubt the maths is quite complex, and perhaps not justifiable ATM.
(https://www.maplesoft.com/applications/view.aspx?sid=34940&view=html)
However if this is something that you have been considering, it could be accommodated in the tool pallet as an option under Contract/Curve/Project as a projection mode menu option "Min. Path". Though a stand alone script would suffice.

I combed through the forum to see if this had been previously discussed and can find no earlier reference. My apologies if you have already answered similar request.

Have a great weekend
James