The instructions say to build the upper decks off the ship and then attach as an assembly. I have thought about it and can't see any good reason for this. It is a problem trying to attach all these warped parts in midair so I attached the promenade deck to the ship. This has at least taken some of the warping out of at least this deck. Now at least I have something somewhat straight and solid to work on. I guess I'll find out later if failure to follow instructions comes back to bite me lol.