I am following the advice, here, by removing an underlayment of particle board. The sub floor is ply though I am not sure whether its 1/2" or 5/8." The joists are 16" OC. My question is: should I add a 5/8" ply on top of the sub floor before laying 3/4, 6" yellow pine blanks? Or, can I lay the planks directly on the sub floor? The sub floor has roofing felt on it.