Thank goodness for Costco. They had a sale on 105 AH Lion LiFePo4 batteries. I bought 2. I contacted Lion and they told me that I can simply use the Li setting on my existing equipment with them. No need to replace my existing chargers and program charging curves. Since Lion offers a lifetime warranty on these batteries, I find it easy to believe them on this. Also, Costco does a good job of backing up when they sell. This also gives me confidence. I will purchase a DC to DC charger to isolate the Li Batteries from my alternator and a cheap starter battery. All this adds up to about 50% more cost than my original plan of purchasing 3 regular group 31 AGM batteries. But, the Li batteries ought to last as long as I do on this boat and give me quite a bit more capacity.
As for my original question about the Carbon foam AGM batteries. I really saw no point to getting them at a slightly lower price point than the LiFePo4 batteries that I ended up with. Less capacity, shorter life and an unfamiliar technology did not seem to add up to a good buy.