Hi all! We are refurbishing our house. We removed carpets. Top floor: Insulated under subfloor with sheep wool, screwed subfloor boards back. Now what should we put on top of subfloor before putting solid wood board? Underlay? Which? We bought green square underlay but originally it was for laminate flooring. Now can we still put it? Also what is the best technique to fix solid floor: glue or nail? Thanks for any advice or comments!