Re: Battery Sizing - am I crazy?
Optima batteries are in a world of their own. They are made by JCI, who are a top maker. They are sprial-wound AGM batteries, and in theory that process makes them much cheaper to build than flat-plate batteries, and more vibration resistant. In practice, JCI charges about a 30-40% premium for them, and because you have round batteries in a rectangular case, you also get about 10% less capacity than a same-size flat plate battery.
And, no better warranty.
If AGM is the way you want to go, I'd go with flat-plate AGM batteries, get 10% more capacity at 30% less price. Last year...I think that was about $200? $230? for a G31 from various sources. Of course the price of lead seems to double almost weekly, for reasons that totally elude me.
And if your charging system can match the, consider gel batteries. Even the AGM-makers are now saying gel batteries will totally outperform AGMs in terms of charge cycles, if you can give them everything else they want.
But Optimas? Mainly, they've been branded very nicely. If JCI would just drop the price and raise the warranty, to match what they say about the technology...