Two issues.

The first, my front cross bar has some small, hairline cracks radiating from the hole where the dolphin striker post goes through. I believe these cracks are the result of corrosion due to the dissimilar metals of the cross bar and the striker post. I am considering drilling a small hole at the end of the crack as I have been told that this can stop the crack from growing. Just wondering if anyone has had success stopping cracks using this technique.

The second issue. My hulls are leaky, I have soap tested them and believed I had found and patched the major leaks. So when sailing the other day, I decided to check the hulls while out on the water. While unscrewing the port cover, I could hear air hissing, so I thought wow, air tight, but after looking in the hull, there was water in the bottom. How is it possible for the hull to hold air, but leak water?
Any thoughts?