Ok, here are some things to consider.....
A prototype is an item being tested for suitability and if it fails is rejected, or redesigned. So, that is where I am right now. I have 2 or 3 designs under consideration.
As for plastic or other? Well, it is SS to effect heat retention, weight stability and abrasion resistance ( for paper units mainly ) and so is still being tested in the face of other designs. Be patient.