The type of double stand im refering to is where you could have two tanks in one spot. Like one on top and another on the bottom. Not side by side. I got all my aquariums in my room so double stands let me have twice as many tanks then the normal stands.
What I meant is that a 120 is basically the same weight as putting 2 55s next to each other. So while it seems like a lot of weight for a wood stand, it would actually be fine.