OK, from what I have seen here the felt will even out the pressure of the plate glass.
Also the sides will be ground to avoid sharp edges. The light source will be 2 evenly spaced bulbs 5 feet above the glass. Azo is slow so a few test prints will be in order.
I'm happy I kept the old Azo rolls after all these years. Still good with no fog. I did not make the negatives. A photographer friend who has since passed gave me the negatives. It seems fitting that I should make good use of them.
If you are not wanting to use glass you can get some clear film type material and use a vacuum frame that is say 12" wide by 6 feet long and cut a 1/4" channel about 1/4" Deep around the outside and drill it all the way through in one corner and attach a vacuum to it and then paint it flat black to take care of any extra reflected light. Then lay paper down then neg on top for the E to E contact kick on vacuum and roll out any bubbles and you have a quick and inexpensive contact frame. I used to have one that was 4'x8' just like that that I used for duplicating very large screen mylars.