Les:
I now have a shutoff for the chassis batteries, between the negative post and its connections. I no longer have any fear of losing charge on those batteries, as had been happening alarmingly quickly when I had to store the coach without power for a few weeks.
The coach already has a cutoff in the DC circuit. Loren, at Bend, ( lorenc@bendservicecenter.com ) sent me a circuit diagram for a 2000 Patriot Thunder, that being the closest she could find to my 98 Contessa. You should ask her if she has one for your 2003.
For teh Solar Panel circuit, the diagram shows it conncting to the "Start Boost solenoid" under the bed.
The diagram also shows the "Coach Power sSlenoid", but not the switch that turns power off. In my coach, and likely in yours, the switch is at the front, in the stairwell, and operates the solenoid, which is also under the bed. In mine, the two solenoids are together.
My original thread illustrates the problems I have had with the Coach Power setup, and I will update there when I am done finding the answers.
Keith