after 1 hour the neoprene will compact,leaving you no better off, the plywood is for floors that ae soft when walking on them, your tank moves, not a good sign. at 55 gal ataching it to a stud is fine, but having a lip on the base is more important then. As for seams earth quakes dont cause seams to split but they can shatter, there is also diffrent types of quakes, having been in many.... the rolling quakes, violent shaking, and the up and down, yea they are not the correct nomenclature, but thats what they do. some you prepare your tank for others it wouldnt matter, I went to a friends home in the loma quake, his home was off the foundation, bricks from the fire place exploded and stuck in a wall 2 rooms away, I love my tank, and I enjoy my home, but in a big one, my home and tank will be in the bottom of the hill, and ill be talking to my AAA rep on replacing the home and contents.