I bolted each battery box down to the skid/frame rails that the original battery case was bolted to.
Then I lined the bottom of each with a battery-acid mat. The straps that are buckled on the top of each case only functions to hold the top covers in-place.
I have thought about a battery disconnect....currently, I just removed the short battery cable between the two batteries, so the circuit is incomplete. If I need to start it, I will just put the short battery cable back on.