Thank you kindly @laurent_delrieu. That code from David was from here?
I hacked it up a little to add more params, though I don’t know C#. It works. The reflection is from setting the Environment (not as obvious as one might think 
).
create_material_2020_Jan12a.gh (9.2 KB)
I’d feel much better about R6 if this kind of hacking weren’t necessary.
P.S. It doesn’t seem to work in Arctic or Ray Traced rendering?