I think the cleats on the rear beam are actually rudder downhaul. I believe that used to be referred to as the Aussie rudder system - one of our 5.8s used a similar system. It gives more control over the rudders, but you lose the auto pop-up the stock system has. The eye straps next to them are most likely for the spin sheet blocks - although they're not the best angle for that (they could also be the dead end of the rudder line). On the port side of your front beam - the little cam cleat is for the jib luff tension.

The mast is a little odd with all the different halyard attachments. The two up top are most likely for two different size head sails. The one below the hounds almost looks like it was put there for the jib - definitely not stock.

Todd is spot on about the jib blocks being on the hull track and losing pointing. After playing with settings a bunch (stock 4-way system and stock sails), I found that for upwind I wanted the jib blocks almost in to the hiking straps and back enough for some jib twist (depending on conditions). For downwind I left the blocks in the same place and merely barberhauled all the way to beam end, for reaching somewhere in between.

I also agree with Todd on the mast rotation control - use it for all points of sail. But don't forget to release it during tacks and jibes... How to rig the rotator - on your front beam on either side of the mast step is an eye strap and a turning block, then a cam cleat at the base of the barberhauler cleat. Dead end the line at the eye, run it through the opposite block on the rotator, back through the turning block, and then out through the cleat. You can run a long line and use the other end of it for the other side. When you're done rigging it, the lines from each side should cross each other under the rotator on the way to the blocks and back.

As Todd said, the cleats on the mast near the downhaul are for cascading parts of the downhaul. I don't use them on the downhaul setup on my 6.0, but we do use them on the downhaul on our N-20.

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