Your stand looks nice, however it is making me nervous. Right now, ALL the weight from your tank is resting on the support from only the screws. You need to cut at least four (eight would be better) more 2x4's to fit between the top and bottom frame in the corners. One on each side of the middle support would be a good idea too. You have roughly 1500 lbs sitting on screws. Please get this done ASAP.