We had a cabin built 3 years ago. The cabin has a loft with 3/4' tongue and groove boards nailed directly to 6X6, 24"OC pine beams. The beam span is 16'. There appears to be some sagging in a couple of the beams. Any suggestions for making the floor more rigid, as it bounces when I walk up there. Support beams below is not an option as it is directly in the middle of our living space.