I've looked through the threads and haven't found quite the answer I'm looking for so I  thought I'd ask here. 

I've got an ISO (approx 16 years old) and I've noticed it took on a fair bit of water inside the hull especially when turtled. I've found what I think to be the main source and that's the bung fitting at the back. The bung casing bit screws into the back of the hull and then into a piece of wood inside the hull, but unfortunately one one side this wood is no longer attached to that part of the hull. Someone suggested to me to just fill the holes and re-drill them to provide the screws with something to have purchase on so I was looking for some advice. 

Is this a good idea ( should I be trying to fix this another way?)

What products would you recommend to fill it with?

And then once its filled is it simply a job of re-drilling the holes and then screwing the screws in?

Sorry for all the questions.

Ali