I had to redo the stand for my inwall tank - 90 gallon over a 75 gallon tank.
Both tanks are 48.5" wide so supporting the 90 gallon on top would be interesting because I wouldn't be able to put the "legs" of the stand directly under the corners of the 90.
So I'm going to run 2X6s along the length of the front, middle and back of the 90 gallon tank. I'm only concerned about the short edges. Do they really need to be above a support?
Here is a video of my plan. *Note that there will be another tank below it*
There are walls on the left and the right of the tank so I'm not concerned about sheer although I will probably put another 2X6 across the back just to make sure.
Will this hold up the 90 gallon tank?
http://www.youtube.com/watch?v=qjN6FO07Rds