3/16 inch plastic is a weird size and pretty heavy for the heat shields. I tried it with 1/8 inch plastic and it works great! Unfortunately 1/8 plastic is way too flimsy for any LST grid, even if I make the ring really thick. After searching through the TAP scrap bin to see what sizes are available, I decided that 3/16 inch is OK for the LST grid and 1/8 is perfect for the heat shields. For some reason 1/4 inch pieces at least 12 inches in each dimension were hard to find in the scrap bin, maybe because they are so popular. TAP has half off scrap on Fridays and Saturdays!
Also when I’m doing the laser cutting for production products I need to make sure that the protective film is on the bottom of the plastic while cutting. Otherwise the plastic has marks on it from laser flare ups.