[RickT]

Not sure about the opens. I found the information about the second drain in my 2001 35' Express by reading the owners manual. On the express, you lift the hatch in the center of the trunk floor, and look aft for a  roughly 1 inch round plastic plug head in the center of the transom bulkhead down about 9" from the trunk floor. (same plug in the center bottom of the platform you remove for winter draining),  I leave mine very loose so any water that drips into the platform from the inspection hatches on top, drains into the bilge. And, the inspection hatches do leak a bit over time. Ignore  this second drain and you could be carrying an extra 700 or 800 pounds in the back of the boat.