[oldfielder]

I don't know why I didn't think of it when you originally posted, but I had the exact same problem on my cc last year. It drove me crazy because I spent so much time thinking about where the water could be coming from in the front of the boat. One day I was on the boat in some rain, took a look in there by chance, and saw the water sheeting down the inside of the transom. That little molded in depression under the tube doesn't help when you lose the seal because the water gathers under the lip of the tube and wicks right down the outside of the tube to the transom.
I'm not ambitious enough to do anything other than seal it up good and keep an eye on it.
Speaking of flex, this was the same time I decided to take a closer look at the forward fish box drain tube, which also takes a lot because it goes between the liner and the hull. Sure enough, the old tube had a decent crack in it. That one came out and in wnet a threaded thru hull. Everyone on the board who has an older boat should make it their work to check that forward tube carefully-seems like it could definitely be a boat killer if your boat was heavy enough.