Hi
Put a fillet of filler on the deck at the join about 100mm diameter before you glass.
This increases the thickness and supports the joint, it also blends in the angle on the deck nicely.
I've never had one break.
With your build I would spend the extra money and get epoxy resin and use just 1 layer of glass.
Poly resin doesn't flex as well as epoxy and will end up cracking
Cheers
Pete