Neil, I realize that you have alot invested in your system and changing is $$$ and sweat. In my view the potential problems with charging a starting battery and a windlass battery from the same alternator introduces complexity. No doubt it can be done by somebody but when we were designing our system I was excited to put the windlass battery close to the windlass till I understood that when I needed long use from deep water or multiple anchoring the current to the battery would require the large capacity wire that made the battery close to the windlass unnecessary. The result was that I wired the Lofrans 1500 watt with 2/0 from the house batteries to the solenoid and somewhat smaller wire for the short run to the windlass since Lofrans gives so little space for wire. Tappan Zee has 2 alternators and I see large current from the alternator when running the windlass even with 4 charged house batteries powering the windlass. I am NO expert though I did make my living for 40 years as an electrician.
Tom Evans
Being a professional does not mean you are good, just that you are paid.