My view is that 2mm sheet aluminium is required to give the tool tray adequate rigidity, given it will be carrying a wheel jack, hammer etc. As DaveW points out this is too stiff to work with easily at home without a press, hence my suggestion earlier. Other TM'ers as well as myself have had aluminium trays made professionally, and all to my knowledge have used 2mm.
To quote Clint Eastwood "a man has to know his limitations"
