i think you could technically take a tank thats atleast double the size and prop one thats half the size on top and have a MASSIVE tank, without the added with, just added height.
idk that would be sweet to see a 300 and a 150 combined
The maximum height a vacuum can be pulled is 28 feet in Denver Colorado.The formula I found for this is dependent on the atmospheric pressure in the location of the tank.
Of course the glass would have to be much heavier, but the forces that apply should be the same as a regular aquarium construction.
The largest one to date is in the Oita Marine Park Japan. http://www.youtube.com/watch?v=S-PBj4_z1-U