Ply 1 inch.
Had water on deck plenty of times , and the door would not be my issue. The water load , on deck , headed into the next amount of water could be. In heavy weather.
Just gotta keep it closed. Glass is not as tough as ply. Glass ( windows )when twisted break real easy. Like what happens on the older FRP boats that have the Fly bridge supported by the glass glued to the light frames. As an example.
Fix the window leaks on such to protect the structure from failure.
From my experience limited as they are its the flex or the twisting of the boat / cabin, that takes out windows and door locks more so than the actual hit from water. While pleasure cruising the coast.