just finished stand and have a problem

[Abbyreefer]

So I just finished the stand brought it upstairs checked horizontally and perfectly level.. sweet I was thinking. then places the tank on the stand and low and behold it wobbles. when the left side is down the right back corner sticks up I would say about 1/8". if that wasnt enough the stand wobbles as well. It seems that the flooring isnt quite level in the house and leans back slightly towards the wall and hence makes the stand also slightly uneven.

The stand I can fix with some slight shims and such my my biggest question is will the tank settle itself onto the wood and even out ? if I used the foam pad under the tank would that help or am I risking too much with the posability of the tank then cracking ?