I have a 2015 233s. In ours the battery disconnect is below the fridge. It's a peg that you pull out.
As far as the mattresses, I email Forrest river and was told the bars should be tucked in the fold of the mattress. There really isn't anything that holds the mattress in. The front bunk, the slide holds it in. The side bunk is the worse. We just deal with it.
ENJOY. WE LOVE OURS!
Jeff and Michele
with 3 kids (19, 16 and 11) and a new puppy
2015 Rockwood Roo 233s
Towing with 2007 Ford F150
Camping in Colorado