Good advice on pre-staining the planks. I am going to do some digging around this weekend to see what is really in the sub floor. I know that from the top side there is particle board and from the underside there is particle board. I haven't figured out if there is something else in between but, I would be surprised (and happy) to find any OSB or plywood. I will post an update once I find out what is in there and what I end up doing. Thanks for the advice.