sounds like you might be missing part of the gooseneck. In the center of the "U" should be a welded Stainless Steel 'box' (old style) with a hole at one end. It should also have a hole 90 degrees to the first one for a pin for the corresponding "U" on the mast. A simple piece of Stainless square tubing will suffice (new style). If you need a piece of this, I'm sure I can get plenty from our scrap bin at work. If you can supply me the dimension of that U I'll see what I can do. See the photo below.

I've seen a ton of variations of downhauls. You can clearly see the gooseneck and a little of the downhaul in this picture. I had two 'headbanger' sheaves and cleats on either side of the mast. A continuous line ran through one, to a triple pulley (micro) on the sail, to a sheave on the mast (see photo), back to the triple pulley, to the sheave on the other side of the mast, back to the triple pulley, and finally down through the other headbanger. 6:1. Be warned, the 8:1 in the Murray's catalog is not 8:1...they'll probably tell you that if you order it - it was a mistake (that we discovered right here!). I really liked my downhaul but the attachment to the sail was a little tricky because of limited space. I think I had a twisted U shackle that I used to directly attach the triple pulley. I had plenty of downhaul but there was not a whole lot of room left over between the pulley and the gooseneck. I've also seen some guys rig a Hobie 20 style downhaul that extended the mast pulleys below the boom...see the murray's catalog for more detail on that one.

For a good while, I ran my jib halyard straight down to the v-jam cleat on the port side of the boat. However, my cable halyard had a small pulley on it and eventually I began running a rope tail tied to the eye on the end of the cable, through another sheave on the mast, back through the pulley on the end of the cable halyard, and then to the V-jam cleat. This gave it a 3:1 purchase. I never felt that I really needed the purchase but it made it easier to adjust while under way.

Oh yeah! note the green bunji running through the diamond wires out to the beams. The purple jib sheets should actually be on top of this instead of how they are shown here. The green bunji helps keep the jib sheet from fouling on all the crap at the base of the mast as you tack.