Extrusion of surface bisector to joined surfaces


I have been building on a code to extrude a surface 20mm on each surface edge bisector to the angles of the joining surfaces. The script seems to work on some angles but not on all, and sometimes extrudes inwards (as required) but not always. After 3 hours of flipping/grafting identifying and all other sorts I am unsure of the next move to resolve the issue.
Some clues or hints would go long way to me solving this problem. thanks for any suggestions.

forgot to attach the file… late night!
TriangulationofSurfaceBissector.ghx (2.1 MB)


Depending on what you want to do next, it can be a way to do it :

TriangulationofSurfaceBissector_re.ghx (2.2 MB)

oh man, you nailed it. I will be able to trim them all back and tidy up the rest.
champion work. thankyou.