Berettaclayshooter
Meat Mopper
If your building a single grate that's 48"x60" I would go with 2x2x3/16" angle with a minimum of 1 center support, but personally would use two, creating (4) sections. Something that big will have a lot of flex and even with 11Ga expanded it would be a mess. Make your frame, cope the two center supports to fit and then just put the expanded on the top. If anything just cut the expanded a 1/2" smaller than the overall giving you a 1/4" reveal all the way around. And smooth the edges with a flap wheel on a grinder. PM me if you have any questions.
-BCS
-BCS