Phantom overnight leak on 96 Sport

Its had a small leak since I got the boat a few years ago. I've been mostly restoring the boat and it only was on the water for an extended period last summer. 

The leak is small enough that it is not noticable, but overnight the bilge fills about 4-5 inches high under the engine. I'm not 100% sure, but I think the water level stops here as I've never seen it get higher.

I've looked all over and can't find the leak. I even filled the bilge with water and let it sit on the trailer but it didn't sow any signs of reverse leakage. 

I added silicone around the exhaust pipe...no change. The drive shaft packing is good and new and is not the souce. 

I've narrowed it down to 2 possible sources....

1) The rudder packing. I commented on another thread earlier today about what is the correct size packing rope, 3/16 or 1/4? Ill order some to have on hand when I start troubleshooting. It was also suggested in that thread I try tightening the gland nut on the rudder.

2) The rear-most tracking fin is bent about 30-40 degrees. Its on my list of things to do to lightly heat it up and try to straighten it out. It is not noticably loose. Could this be the leak? It showed no reverse leaking when bilge was full and boat was out of water, but maybe that doesn't mean anything. I assume it is caulked with 5200 which I've heard is a bear to remove. Should I try to remove the fin and re-attach with fresh 5200? I'm guessing the rudder is the easier path to pursue first?

3) Its also not the muffler. There was a small crack on the bottom that I have done a fiberglass repair on.

4) Any other ideas?

Thoughts?!!

Picture for reference.

1) I do not remember how I determined it was the rudder packing.  Did it in 2013.  Figured it was something that needed doing on my 20 year old boat (at that time).  Yes, it solved my leaking problem.

2) Yes, you would have to pull the tank to do that.  Are you installing an extra exhaust hose and thru hull exhaust port ?

3) Pulling the gas tank is not that hard.  Have to make space to pull it forward.  Remove straps, Fuel lines (one going to the fuel pump and the one for the  vent hose.  Also removed the wires for the fuel gauge sending unit).

4) It is my opinion that if you are taking the time to pull the fuel tank.  Go ahead and replace the rudder packing.  Don't just tighten the nut; you will have to come back later and tighten it again.  Think you are due for new packing on your 26 year old boat.   Repacking the rudder is pretty easy.  Remember to support the rudder from underneath the boat so it does not slide down and out of the port once you loosen it.