All of the fire ratings you see on building materials are based on ordinary combustibles. Most of today’s products are built with highly flammable materials that burn hotter, so a 30 or 60 min rating is only good for less than half that in the real world.
translation... your couch, bed...
Not sure about costs, but optima has gone down hill. There are a few good posts in the last few months about batteries. I just got X2 power from patterned plus.
but all this will be worthless if your billet battery boxes are for optima