My standard tray design creates a 3" deep tray area. I find this to be cleaner than a flat "cookie sheet" type tray. It allows you to use the mulch method (vs. cage paper).
Very large trays are sometimes made in two pcs. The foor is 22 GA. cold rolled and the lip is 16 GA. cold rolled. It weighs an average of 20 lbs. To date, (15 yrs) I have not had to replace any trays.