That is a little unsettling PM, I do hope it all works out for you.
My tank will be built by my husband who after I posted this asked, why can't I build the tank as a "sectional"? He spent some time on Solid works making me a drawing so I could understand and making sure the gaskets would hold as we want.... its all good.
Looks like he's made up his mind. The tank will have a seam running the length of it and a monsterous pair of gaskets in the seam. The current plan is for a 8x3x3 which will give us a little over 500 gallons. The beauty of the design is that it can be taken apart if we ever decide to move, and if we ever decide its stimply not large enough he can add an extension into the seam and make the tank as wide as 5'. An 8x5x3 tank would hold closer to 900 gallons. I don't need or want one that big right now, but its nice to know I have options for the future.
Now we just need to find the money for building supplies.