best bet is to securely bolt them down. using 3/8 threaded rod, and steel angles. keeps them from bouncing around.and just makes it hard to remove.
i have 4, 6 volt batt, and use this bolt approach between each batt, and secured to the frame work at one end. O and "lean" the bolts inward to help hold things from shifting.
if your really crazy a new specially build access door and door frame. made of steel. and secured with "better" hardware than factory. but then that screams look here.
maybe a alm or steel grating inside of the access hatch bolted to the coach body.
but if you are leaving the coach someplace for a month of two, the creeps can test and see how to get past anything, to strip down your coach.
best thing is invest in a online live time video cam setup. this way you can at least see who did the damage to you.
