I do not have HW flooring yet, just subfloor (3/4 T&G Fir dated 1929). We removed a couple of pieces to assess how the boxing could be done. That is when I figured out I had only a joist and not a real beam to work with. I would love to hire a pro but nobody wants to do a 48" long baluster. I cannot see your pictures. It looks like you attached 2 images but they are not shown. Thanks