We are about to replace some old worn out carpeting with hardwood floors. We have a plywood subfloor, then on top of the plywood is a layer of pressboard. Some contractors have told us that they can nail right on top of the pressboard, that it won't need to be removed. Others say the pressboard will need to be removed, and then they would nail the cherry oak floors onto the plywood subflooring. HELP! We are not sure which way is best. With longer nails, will the pressboard actually aid in holding the floors? Should the pressboard be removed?