The rub rail on this older CAL sailboat is very sturdy and quite stable so what I did is, after I put masking tape on both sides of the joint, ran a bead of caulking about a quarter inch wide from stern to bow, actually two beads of caulking, one above the rub rail and the other under the rub rail against the hull side. What happened is water ingressed making its way through the rub rail and through the hull-to-deck joint (which is no longer totally waterproof), this happening when the boat heals under sail in a stronger wind. Going to the extent of removing the rub rail altogether and addressing the hull-to-deck joint leaks would assuredly be the best solution but also a lot of work and would entail replacing the older rub rail as it is always difficult to re-install very old ones. Granted the caulking I put could also leak at some point in the future but I is always easy to just re-caulk. A lot of the problems with older sailboats (I found) is that the caulking used is good for about 30 years (including the 5200 used to bond the hull-to-deck joints). Also it is very important to remove the insert and re-bed every through hull bolts holding it.