Years ago I built two identical wooden stands for 2 50g breeders, with 30gals below each. One ended with gaps similar to what you have.
I thought it would be ok, specially with the smallish tanks. Well, it was ok for a while. About a year later, in the middle of the night, I heard a big noise. Went downstairs to find the front glass had cracked in a semicircle shape, and water slowly oozing out.
Was it because of the non-flat stand? I don't know, but it certainly was that tank and not the other, which went on for several more years with no issues.
Will yours be a problem? who knows...but 220gal?... I would put some foam layer and a piece of thin wood such as plywood on top, then the tank on top. Any deformation should then be on the foam.
Good luck.