I am a fan of teak,and teak covering boards done right would look great.IMO I would use one length down each side and one across the transom,mitered to fit each joint so you wouldn't need the black caulk.You can grind off the gel coat and bed it in epoxy and cabosil screw from the under side with temporary screws and washers to hold it in place until the epoxy sets.Once the epoxy sets remove the screws and it's there forever.I've done it on a couple boats and I'm getting ready to do it on a custom carolina boat that a buddy and I are finishing.Don't stop with the covering boards,put a teak toe rail on her as well!