Steve,
Your cannon and their rigging look fine to my uneducated eye. In which books or what references did you look to find the rigging of the cannon? I can't even remember if the instructions showed how to do it - right now I'm tired and too lazy to pull the box down from a shelf in one of my "stash" closets.
I guess when I get around to building that kit - if I ever do - I'll use this guy's model as a kind of reference for the rigging of the cannon if I can't find it in one of my books. BTW, this guy really seems like a master at model building. His name is Dmitry Shevelev.
http://shipsofscale.com/gallery/dshevelev/french74/index.html
I don't know how accurately he's built his French 74 - I'm sure John Tilley would be able to comment on that, but his technique is, in my opinion, laudable.
Anyway, I'd appreciate knowing how you figured out how to rig the cannon. They look really good to me.