There are some other pics of my exsiting caprail situation on an earlier post in the maintance area. I'm not sure what is exactly there and how the hull to deck/joint is formed . I feel sure this area is foam filled .It might have something bonded between the hull to deck joint to screw to at the top .The deck that I stand on is about 2 foot lower than the caprail area.I'm pretty sure about the width being around 1",that's the main reason I wanted to add the stringer to the inside also .My cap rail is leaking in a few places now ( lot of the stringers are rotted at the end grain,I think they used mahogany) and the water finds it's way somehow to a bulkhead and spils out on the v berth floor. I thought everyone used some kind of cauking under the caprail. Take a look at the other pics if you have time.