plywood choices for floor and transom

[RidgeRunner]

Good choice. The price is right. We pressure treat plywood on a regular basis. Arauco plywood is one hard plywood to treat. It has interior plys that are so dense we simply have trouble. The interior plys are also allowed to be hardwood which cannot be penetrated effectively by the pressure treatment process.
On the other hand, Radiata Pine boards and fence picketts are like a sponge. Due to the fast growth of the tree, the growth rings are not very close together so there is a lot of sapwood that is easy to penetrate with preservative.
I don't think you will have any issues. It has a great track record. Keep us posted.. Pictures too..