i had a similar pinhole leak, air came out around the cosmetic button on the bottom when hull was pressurized, and water came in even on completely calm days (slowly).
The problem is that the fitting into which the stud holding the mast base screws is molded into the hull. To do this, it has to screw onto the mold; this leaves a hole, which covered by the cosmetic plug. Inside, the plastic is scraped away on top of this fitting so the stud can go into it. Usually, the plastic is tightly molded to the fitting and does not leak, but it can loosen up enough for water or air to pass by
The fix was to remove the cosmetic button and plastic weld the opening it filled closed. Now it does not leak, and the bottom of the boat is ever so slightly smoother, making it almost as fast as a red boat, even though it is yellow.