With a 108 lb outboard, the C250 wants to squat on her stern.  Cruising requires more than the single group 24 battery in the aft compartment.  R&R has two six volt golf cart batteries in the V-berth locker helping boat balance and aiding checking the batteries.  With some degree of concern about how this was done, I made a battery box rather than try to contain two plastic boxes. 

With some concern about the effects of 140 lbs in the bow when it pounded into a trough.  It seemed necessary to distribute the weight and hold it in place.  For this reason the box was mounted to a piece of plywood cut to fit within the hull sides.  Carpet pad is used beneath the plywood to address any imperfections in the locker surface and add cushioning.  The lid drops within the box to the top of the batteries with a loop of line exiting the hole where the block of wood turns and tightens the line....securing the lid

btw...The six volt batteries are doing well having finished their 5th year of service without problems.  They are heavy duty with a good amount of water over the plates and won't go dry unless grossly neglected.