I went through this and was not really happy with the plexi outcomes. They always needed to be reinforced and would look "crafty" as a result. I like 18 ga diamond plate:
It stays rigid up to 18" before it needs to be reinforced with angle ali. If you specify a measurement to the metal shop, like you will not take the shelf if it is not made exactly to spec, then they make a shelf out of one piece that will straddle a bucket, or a fader throw or whatever. There is weatherstripping on the bottom edges, but I plan to use commercial grommets in the future. If I put velcro loops the shelves slide nicely.
I'll get a pic of a nice 9K shelf.
Mike
