Yes, I have used MDF-faced plywood, it's a product typically used for building stages or for laminating panels in cabinet construction. It was on odd thickness, like 11/16", it's called "Pro-core". Can't answer for the 5 x 12 size, though it's probably available in MDO. I purchase from Royal Plywood out of L.A. area, they are knowledgeable and should be able to answer your question.