BuildVolumeMesh issue

[_Aka_]

Using a Variable Shape Mixer Or the X Multiplier under Scale of the Shape Extrusion module to control the width of my track profile I'm still left with a problem. I still need to create a guardrail.

In the 25_CGExtrusionAdvanced you make a Shape Extrusion 'wire'. This wire follows the spline, just vertically offset by a fixed amount using a TRS Mesh module.

But a guardrail needs to follow the extruded cross-section's width. This width varies based upon the Shape Extrusion via one of the two methods described above.

I'm still unsure how to do this?

I'm sorry if I missed your explanation previously. I should have separated all these issues as they came up.

I wad thinking of using the Variable Shape Mixer to mix two shapes, both with guard rails. For example:
   
These shapes are very simplified. Maybe your real use case can not be achieved with the solution I am suggesting. If it is the case, let me know and I will talk to you about the last resort solution.