verruckt;4144913; said:went out to the garage and sit in the tank and used my legs to push against the back of it as hard as i could, nothing popped or cracked but the center of the plywood did bow just a little, maybe 1/4" tops. so ive decided to add 3 braces to the center and 1 or 2 on each side. i guess to make everything smooth i wlll go buy some 1.5" foam to put between the braces on the side and back then fiberglass it. extra insulation never hurt.