Overengineering is an EXCELLENT idea when you're talking about, oh, 700+ lbs of weight and live critters with the no-fun-at-all threat of a catastrophic flooding.
Never hurts to be safe vs. the alternative of sorry. You should see some of the overengineering my father has done for tank stands for me! Downright silly. But I can say I have NEVER had a problem with anything failing (or even thinking about it!).
Slapping some pieces of 1x3s in the gaps would be a simple way to get some peace of mind. Looks like all you should need... it really is shocking what passes for a tank stand anymore.

It is not murder if you're killing snails.