Thanks for that Grendel. However that would translate to glass 40mm thick and 240mm diameter, in full size. I had used 2mm glass for my 1:7 scale Windermere steamer, Branksome saloon, which is too thick but was the best I could find at the time.
I am quite excited using the cell phone protector glass which is about 0.5 mm - ie 10mm full size - thick on ML 167.
I have used it to glaze the wheel house. It is super fiddly as, although it is toughened, it is fragile once the plastic layer is stripped off.
I have had to strip the plastic to break/cut it into required sizes and to be able to glue it.
My test porthole tube of brass was faced off and glued to the irregular piece of glass with cna glue. Once the glue is set the excess glass is ground away using my bench top grinder to leave the porthole tube with a scale thickness glass pane on the inboard end.
UV acrylic glue is expected to be better than cna as I can apply it more accurately, curing it as I go and there seems to still be a 'surface' on the glass that does not bond as well as you might expect with cna glue.
I love the research as much as the building!