I made giant shims out of popular wood. I bought various thicknesses (.25", .5", .75" and 1") and used an electric sander to ease the transition between the different sizes. I used wood glue to connect them. I then painted the shims using a high gloss paint to protect them from water/spills. So far they are holding up great. I think the fact that they run almost the entire length of the tank helps. In other words, if all that weight was on a little 2" shim on the low end of the tank, then it might cause problems. But since the weight is distributed evenly across a span of over 9' on both the front, back and the 3' end of the stand, I think wood shims are ok.
Very nice and proffesional very well made ,,, like you my floor was way off and I was able to do a full piece of wood on one end and and I made aluminum shims for the rest,,, thanks for the reply