Sorry if this is a stupid question but what are vertical supports?Always use vertical supports to support the weight. Cory from aquarium coop built the racks in his store with the method you are referring to, but it was for smaller tanks, and he used large bolts instead of wood screws. He has how to videos on his channel. You could make the stand a bit wider to accommodate the vertical supports easily enough. And listen to the advice about space above each tank. I built a dual stand for a 75, and 40 breeder. I think I left 10 inches above the bottom tank and it works, but still tight at times when cleaning.