I do not know if there is any interest in this thread, but have only just come to this site. I am a former Thames Sailing Barge skipper and may be able to help on some of the issues raised above.
The jibs on the model. Yes, the outer jib, the jib topsail is upside down. The topmast forestay on which it is fastened should go to the top of the mast. The stay for the middle jib, the jib should co to the lower end of the topmast housing, not as suggested the top.
The heavy chain across the deck is inaccurate. There was usually a steel plate bolted down to the deck, then rods coming from that on each side connected to a short length of chain which went through the pivot point of the leeboard and was held by a three curved prong fitting through the chain. Leeboards were raised and lowered by a crab winch on either side, well back abaft the main horse. The wire from the winch went through a pulley on the outer edge of the deck and down to a chain through a small hole in the top of the after most end of the leeboard. They were raised and lowered depending on tack, with the weather 'board up and the leeward one down.
Most barges in latter years has screw type steering.
The light chains going from deck down to outer end of the rudder
[size=78%]were kicking straps and were tightened up after anchoring to stop the rudder slamming around and making a lot of noise in the aftercabin.[/size]
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[/size][size=78%]Any questions about barges, please feel free to ask me..[/size]