see above.  cage's script (in python forum) allows designation of path in poser, preview to determine interpolation method, then extrusion of circular cross-section.  should allow generation of co-axial tubes (given same path used), but haven't tried that yet.  P8 or later.

was thinking of HCl release during PVC combustion.  cyano-acrylates (used with ABS) aren't cyanogenic - I double-checked.