Just search LEATHER @markwarfel .
Several discussions on it. I am not planning on using it a lot but have picked up several clues as to good/bad, just from browsing the forum here.
https://community.glowforge.com/t/proofgrade-only/6046
examined proof grade items and also talked plus and minus of leather types.
Another one I enjoyed walking through is here:
https://community.glowforge.com/t/all-about-leather/943
Hope this helps