Hi Andy, the other thing that's pretty difficult in your original one is even when the curve tangents are tuned up, the way it's set up here has a quite complex intersection between the pieces (here shown during a mesh export done to a very high density using "Divide larger than" to analyze the surface shape interactions):





It would probably help if the rail's curve tangent aligned with the z axis direction a little bit before the end of the curve instead of only right at the very end of the curve. That would probably get the surfaces to be the same shape near the top rather than the different shapes for neighboring surfaces like shown above.

- Michael