Re: Question about unevenly-sized battery banks
You already had unevenly sized banks when you had two G27 and two G24s. The batteries in a bank are hard wired together and appear to the charger as a single large battery. The fact that you have one battery in one bank and two in the other is unknown and irrelevant to the charger. Also since you're going down in capacity you'll be fine. The more complicated scenario is if you had different battery chemistry (ie gel in one bank and lead-acid in another), but uneven bank capacity should be fine.
1979 Contessa 26