That tank is awesome.
In regards to the stand, I agree with XXblwn408.
My main concern with the stand would be the 2x4's that you have supporting the middle of the tank, running the width of the tank (from front to back). It looks like they are laid flat (with the 4" side of the 2x4 facing down). In order to provide more strength, the 2" side of the 2x4 should be perpindicular to the ground and you should double them up. But to be honest, if I were you I would take XXblwn408's design and use 2x6s in place of the 2x4s for the middle support beams. With such a wide tank (4') and with that much weight (over 3 tons!) you should use 2x6s. Especially since you are using a sump so you probably can't place a support column in the middle of the stand.
I'm not an engineer, but I'm almost certain that you are going to have some serious sagging in the middle of your stand unless you make some changes.
Sorry if I sound like a hater, but it would be a total pain if you were to set it up and find that it starts to sag, only to have to drain it and change the design.
Can't wait to see the tank up and running. Please post pix when you get it setup.