cool solution. We had rotten wood in our "shelf", so cut open and then rebuilt with G-10 in place of the plywood, turned out rock solid. I think it is bridged to avoid undue pressure on the encapsulated keel. At least on ours, as that puts the pressure on the turn of the bilge, a strong anchor point.
Also noted you have a different mast section, our is Kenyon.
Also noted you have a different mast section, our is Kenyon.