Nice photo.
I'm pretty convinced ~80% of the time water is only getting in there from rain, considering less than 20% of races are in big breeze or waves.
Just convinced? You sail mostly in saltwater ,have you tasted the water in the hull? Fresh is rain, salt is leaky boat. Simple really, a gifted mind such as yours has a better way I'm sure, like a salinity tester. Don't forget to get samples from inshore and off at all regatta sites to narrow down your leaky regatta location.