through hull drain tubes in the floor

[McGillicuddy]

Like I said - a dozen ways to do it. I'm not sure about Avian's scuppers having a nut to cut, but I'm sure plastic is fine... most of the plastic thru-hulls I found were too short for the application as the tube itself needed to be at least 3-5/8" in my app. I think Bigshrimpin used pvc pipe or tubing on his scuppers. Someone else used bronze ones.

I not so smart so maybe someone can explain but are you saying that the outside of the scupper has been glassed in and now your cockpit drains in the bilge?

I don't think I said that... but
What I said about the seal is that when the tube separates from the wood block it creates a leak point. Water penetrates, soaks and rots the wood block and eventually travels down the hull and/or stringer into the bilge.

By overdrilling like Bushwacker did when you fill the holes with thickened epoxy you effectively make a seamless bond between the fiberglass hull and the fiberglass floor. if you now re-drill a smaller diameter hole the new hole has fiberglass walls, now the water has no way to seep into the bilge unless it first comes into the cockpit/deck.