Read my resto thread and you will see the drain/limber holes I added so if water ever gets under the deck it has a way to the bilge and gets pumped out.
Reasons why your stringers rotted
1 neglect.....letting the boat fill up with rain/snow
2 penetrations through the deck.... everything bolted/screwed to the deck has the potential to let water get below deck
3 poor glass work on the stringers from the factory.....they really don't care if it rots..... you'll need to buy another boat.
Thats just a few to start....
How to keep it from rotting again!
When you do you repairs you will add passages for water to escape
You'll do better glass work than the factory

All the screws the penetrate the deck will be coater with 3M 5200 sealer
YOU won't let water stand in the boat for long periods!