Here's my $0.01 worth: Rather than laying the beams starting from the bow or from the stern, I suggest starting, with the beams in front of and behind each mast location - start at the foremast, main, and mizzen mast areas, then install the beams alternating bow-then stern from each mast location. This way, any errors are not additive, as Russ explains, especially if the errors affect the positioning of the masts; actually, should do the same approach with any structures such as capstans and anchor bits, that pierce several decks.
Alex R
Alex R