Al and Mike-
While I'm going to wait awhile myself to see if my new, more supple polyester rope to chain splice passes naturally through the unmodified or assisted windlass workings, I also am thinking the spring steel additional finger is the simplest and most obvious solution if additional mechanical help is needed.
The stainless spring will have the following advantages:
1. It's simple and easy to build. No complex parts to fabricate, maintain, or operate. We all can build one without a machine shop, etc.
2. The shape can be changed by bending as needed.
3. The tension can be adjusted, also by bending.
4. Tension can also be applied (if necessary) along a larger area of the curve.
5. The shape will conform to the windlass shape and the addition will be largely hidden.
6. The spring need not push excessively on the existing finger all the time, saving wear and tear on it and extending it's life.
7. The spring can be mounted along side of the windlass, without drilling holes in it's base. Mike's right, it could be slip mounted under the edge of the base, but there's a gasket seal there that, I , personally don't want to compromise for the sake of preventing water intrusion.
What I'd prefer to do is to mount in along side and somewhat to the front of the finger so that it could push on the finger when it's displaced by the larger splice and then also continue around the windlass to help the splice further mesh with the teeth of the gypsy.
I'd make the device in two parts, a 90 degree based bracket to mount through the deck on the bottom, with the spring mounted to the vertical portion. This would allow the base to be made of any of a number of standard grades of stainless, while the replaceable spring would have to be made of a suitable stainless spring alloy. Acorn nuts on the inside of the spring mounting would prevent snags. The through deck machine screws could be #14's and the spring screws # 12's, as a guess.
Round off and finish all bracket and spring corners, and bend the front (leading edge) of the spring back (open) to prevent snagging.
This sounds like a lot of fun! Working on it is one of the best parts of owning a boat, at least for some of us. Now I'm going to have to go out and start rounding up the parts and playing with the fabrication, even though I 'll hold off on installing it until I'm sure it's needed on my boat.
Thanks for all your help in thing this through! Merry Christmas All!