Just to close the loop here - a brief update. I finally went back to my stock battery. I had a low voltage warning until my first long-ish drive. Since then it has been gone and there are NO problems with CA nor with the date/time memory. Problem cured as I much suspected it would be.
Does anyone know of a battery by BWM or their battery supplier that is lighter, the same form factor and about 60 Ah or so. This would be a great replacement for those of us in warmer climates looking to save weight without any reliability problems.