Good questions Hoppy...
Being a plywood tank, I believe it will be stronger and more resistant to bowing, contortion, etc if the tank and stand are not only connected, but actually the same pieces. Simpler too... Rather than dealing with a "stand plywood sheet" and a "tank plywood sheet" there are just single panels for the sides and back. The tank bottom is the stand ceiling. If I had two pieces, yes, easier to move around, but I would have to line up holes and so on.
The plywood continues all 96in to the top. Like I mentioned earlier, this is supposed to be a single piece of furniture, and I will extend it all the way to the ceiling. That way it will look more "built in", and if I put doors both on the stand and above the aquarium, the actual depth will be hidden. Just thinking it might look interesting, with regular bookshelves around 12", but in this case it contains a 30" tank. I will create shelves and such above the tank to store office things out of sight... some folders, a printer, etc.
My theory for moving it into place (without glass!!!) is to attach a pair of 2x4's to one of the sides, and slide the whole thing from the garage to the inside of the house. Yes, I measured my doors and they are 36x80, so the 30x70 box should fit through... I hope.
Once inside, I will need to stand it up, slide it into place, mark where the overflow to the adjacent garage will go, then slide it forward, lay it down, silicone the glass, let it dry, ask a bunch of neighbors to help lifting it vertical again, and then slide it into place.
Well... that's the theory.