Well, first see what you have under your crawl space. Then think.
8.8 x 360 = 3168 lbs of water. + about 360 of gravel. + stand. If the stand is 200 lbs you still are a far cry from 7000. Your at 3728 lbs.
So take this into consideration when reinforcing the floor. You may not have to do much but you won't know until you get under to see what the construction of the floor is. "Much" is a relative term...............
JFI: I used to design and install high end reefs as well as just a few, big, almost totally sustainable fresh waters systems. This was a few years ago so I may be a bit rusty but I still remember a lot.
Now your tank. It's length is important to how the weight is distributed.
Is the tank custom made? Is it 4' long, 6' long or is it 8'?
Is your sump going to be under tank or in another room/ closet? your sump could be 40' away if need be. The water doesn't care where it flows from.
Let me leave this for now. Get back to us.
I like your idea...a BIG tank is so much easier to maintain.