Update on those cockpit drains. I now know why they are in two pieces, sleeved together. There is a lot of flex in the cockpit floor and the movement makes it impossible for the one-piece rigid tubes in my boat to remain sealed at both ends. I'm either going to open it up, cut out the middle of the rigid tubes and put flexible tubing between the cockpit ends and the hull ends, or replicate the tubes-into-the-cups setup, or just live with it and drain the water after every sail. (Most likely).