Help with DIY stand design.

I have recently decided to build a stand that can hould a number of differnet size aquariums. I have decided to do this because I am planning on buying a 125 gallon of bigger aquarium within the next year of so. I also need to build a stand for my 2 55 gallon setups before I have ot move at the end of July so as to make my moving transition easier. Anyhow.
I have decided to kill two birds with one stone by coming up with a stand that will support my future 125 gallon, but will also allow me to display both of my current 55gal setups and save a little space at the same time. I took my design from several different places, starting with yankz12603's thread over at Cichlid-Forum.com Dual 55g stand?. I've also looked through some of the DIY stand threads here at MFK.

I really need some opinions on this design. I'm no engineer, carpenter, or anything like that so I'm not sure how sound structurally this would be.
This is the Front view of the stand frame:

As you can see there is no support in the direct center. I want to leave this out so that I can display one of my 55's on the bottom with the other on top. I'm not sure if this is possible with such a long stand. I'm certain that if a 125 were to be placed on top, then I would have to install a center support.

Here is what the top and bottom of the frame would look like:

As you can see I plan to add more supports towards the center in the back, which is probably overkill but I'd rather be safe that sorry.

This is largely based on this design provided by venustus19.
The red 2x4's in my design are analogous to the A's in venustus19's design pictured below, and the aqua colored ones are analogous to the B's . The rest is self explanatory.


So any carpenters or engineers, or whoever out there please let me know what you think and please help me any way you can.

Thanks ahead of time.

Eventually there will be a 125 on top. For the first few months I'll have another 55gallon up there, until I get something bigger. And probably some lamps and maybe a 10 gallon or something. Its going to be in the living room area. I current have been using a corner desk with each of my 55 on one arm of the desk. I'm moving to a place with limited floorspace and having a stand that can go along one wall will be better.

I didn't mention this in the orginal post, but I plan on putting plywood down on both levels and around the sides. I'm not sure if that makes a difference of not, but Its for aesthetics more than anything.