I have the perfect spot (so I thought) for my new 40b tank. The problem is that the floor in this spot is very unlevel. Looks to be about a 1/4" or so unlevel. I overbuilt a wooden stand for it using 2x3's. Stand is very sturdy and level when placed on level surface. I'm just looking for some suggestions on what to use to put under stand in order for it to be level before placing tank on it. Thanks.