I am building a raised hearth pad to put a Morso 3440 on top of. I have 2x4 framing in place now and about to put down plywood, then a sheet of durock and tile over that. I have some OSB board laying around, 1/2” is that ok? I think a 3/4 plywood would probably be better but I have the other stuff here and would be nice to use it.