Hello Chris ,
If I am not wrong, flat clean copper plates are expensive. And I have no idea to use of gelatin, I think it uses dicromate and It is dangerous. PET and polyester are different things as you know and polyester is weak to acids. Thats why , polyester based glass reinforced plastic boats are tends to osmosis.
The good thing about printers , if you can select the screening technology , it gives different taste at the final end.
I think working with gelatin is immensely old , nasty , results and densiometry is makes me itch. This process is damn simple and gives 3D relief also.