My stand is built for my 260 gal 96x24x26 tall acrylic tank. I have seen many ppl say you need to add a piece of insulation (like you put on the outside of a house)under the tank to fill any voids. Is this correct? Or can I set tank right on ply wood top? If I do need to add a piece of insulation under the tank which type is best? I have seen the big box stores have 1/2" green sheets. Is that the type to use?