I dont see it as a problem. I've seen alot of larger then 8' tanks as a 2 piece construction. Industry standard is 8'×4' on acrylic sheets. You can find 10' but they are almost the same price as 2 8' sheets. I can think of one I saw with a black back it was a reef set up it spanned the basement wall of a guys house I went to buy coral at. It didnt look weird at all. I do remember him saying the back and top had 3 pieces the front and bottom 2. His was 12' × 3' tall I dont remember how deep but was around 3' I'd guess, it was 3/4 or 1" thick . He said it had been running for over 10 years. No issues other then some scratches. It was manufactured I dont know by whom but it was made by a company and shipped to him.
There is a company that will come and build an acrylic or glass tank to spec in your place of choice. I havent got any info, I found it on a google search a few years ago. If they are still around you could try contacting them to see how they would tackle a long tank. I think the starting prices were in the 10s of thousands. They went all over the world and I think were based in NY area. Their website offered alot of info without having to call them, I just searched for it but couldnt find that same one but I found alot of them around now. Good luck.
