transom/stringer replacing

[twkjr 1250]

I have a unique situation, my stringers are completly hollow and when i took a 3"hole saw, 1" from the bottom ,16" from aft looked inside not even a sign of any wood . Thefiberglass is 1/4" thick at the lap joint of th stringer and over 3/16" above the hole . if i dont need to redo the stringers, how do i go about replacing the transom. I have read a bunch of threads and havnt run across this situation pics included if you need more of certain angles no problem.