Depending on how much deck you need you could do this movie set style. Just build the section you need for filming. Maybe say 1-1 1/2 feet of hull, with a partial deck and the water beneath. Like a cutaway section. That's what I'd do if it were me. Unless I planned on displaying the freighter afterwards. No point in building more than you need. And you can always go back and add to it later on.

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Of course that's just my opinion, I could be wrong.