I started with five split rail fittings and had 1/4-20 flat head bolts welded to the side of each one.

For the anchor hanging bracket I used a piece of scrap stainless steel sheet (I scrounge this kind of stuff from scrap buckets of friendly welders - saved a lot of it) to adapt the hanging bracket to the rail fittings. At the back (sternmost) end of the bowrail, where a mid height rail is welded to the main rail I put on three rail mounts, marked and drilled holes in the SS sheet. Using two nuts and two washers per stud the SS plate is held off the bowrail a little bit. Other holes are drilled in the SS plate to bolt on the anchor bracket. When this is all assembled and tightened down it makes a very rigid mounting point.

The other split rail fittings are for the chain tensioner. Used these to bolt the tensioner forward on the mid height horizontal rail mentioned above. The tensioner is spaced so that it hooks to the eye of the anchor shank. The tensioner I used has an Avibank type pin to prevent it from opening.

As a safety I use a a very heavy duty cable tie through the anchor shank to the rail. In an emergency I could cut the cable tie with a knife. I also split some plastic hose to keep the anchor shank from rubbing on and scratching the rail. Also, when I use these split rail fittings I like to coat the inside - the part that is in contact with the bowrail with TefGel. Otherwse salt water sits in there and causes corrosion.

I hope my description works. Please ask questions if I didn't make this clear. If you are patient I could take a few pictures and post them here. The boat is forty miles from home and I won't get up there for at least a week.