I had my old 55gal on a set of cinderblocks which I covered with pleated black fabric - it looked great! I lined up the cinder blocks, then laid a cut-to-fit rectangle sheet of 3/4" plywood on top of that (to provide a smooth surface with some compression for the tank stand to rest on), put some shims in place to level and fix any gaps between the stand and plywood, then I stapled the fabric in a pleated manner into the plywood.
Of course I did this simply to raise the tank height so it looked good behind my bar. I had no storage under the plywood as I completely filled that space with cinder blocks - which wound up being alot of wasted storage space.
When I moved to my 90G, I built a platform out of 1" wood to raise the tank and stand, but which would provide additional storage. Here are a few pics of that.
The light-colored lines between the tank stand and the platform in the front and on the side are the wooden shims I used to level and fill gaps between the tank stand and the platform. I later pained those black. Looks awesome now and is very stable (I can push on the side of the tank and there is no give at all).
Of course you're planning to raise your tank much higher than I did. That will result in a higher center of gravity, and thus will result in less stability. Do you live in an earthquake area?
I'd just do it and see how stable it winds up being. Cinder blocks are cheap so if it doesn't work out, no big loss.