if you gonna make the stand smaller than the tank have the mop ready, the weight of your vertical panes of glass are all on the edges unless the have one hell of a base i would not advise it.
What you could do is have your counter top extend over the stand and let your tank rest on that, but use a decent thickness top and try and brace it somehow, timber under its own weight will eventually sag leaving a gap between the base, styro and counter top.