I need 1 1/2" of subfloor in my bathroom to meet other floors. Can I use two 3/4" OSB? And will that be strong enough for a freestanding tub? The Joists are 2x10 and average out to 16 oc (self built, I don't think he was too concerned about spacing). Do the layers run the same way, with offsetting joints, or opposite? We are putting down Premium Vinyl planks.