Cage, I have discovered the severe bug that caused the error message. The bug is that I am an idiot. I simply had NOT understood that I need to overlap the two faces! I had loaded them, then very naively I had translated one of them apart "to see them better". Basically I thought that axis translation was irrilevant.

Now I have them properly aligned and the script is doing its job. I cannot yet say anything about the quality of the result because it is still analyzing the meshes, but tomorrow I'll keep you informed (it's almost midnight here and I desperately want a bed).

This project definitely needs a tutorial and an help file. Let me think... I knew someone who worked as a documentation technical writer and was skilled with RoboHelp... who was he? Mmmm.... wait a minute.... oh, yes, I remember! It's me!   Can I help?

Giorgio

giorgio_2004 here, ksabers on XBox Live, PSN  and everywhere else.