Ooooops ... Don, I apologize! I misunderstood SiO2 batteries to be lithium ion batteries.
I prefer Group 31 size in any type battery I might use since two of them fit perfectly right under the step where Winnebago intended them to be, so why restrict myself to using only a couple of Group 27 size there? I don't think that the lithium ion brand I referred to comes in a Group 31 size (not sure on this though), so to spend the $$$$ for them in only Group 27 size would be not stuffing the available space with as many AH as possible.
I think that my coach battery interconnect solenoid connects the chassis battery in direct parallel with the coach batteries, so there's nothing to protect the alternator (?) from getting really hit with high initial inrush charging current if I were to drop in Battle Born Li batteries, from what I read about them - but you're talking about SiO2 battereis, which I know nothing about.
I rarely charge my big AGMs "fully" when camping. I rely on the drive home or RV storage at home to bring them to 100% using the low and slow method. The only time they see 14.XX charging volts is for a little while right after I start up a cold V10 alternator. ;)
P.S. Why aren't SiO2 batteries talked about more in the forums?