[untamed]

You can have a look at my tank build thread. I started working on the overhead doors at the bottom of pg. 1.

http://www.canreef.com/vbulletin/showthread.php?t=28436

I'm thinking...isn't that going to make a 2 foot thick wall? (at least)

Re Question 4: - my first impression is that you need to create some flow somewhere lower down in the tank. I can see a lot of surface movement, water going down the overflows, but anything on the bottom of the tank will likely stay there. Bring one set of overflows nearer the bottom, that way you can shoot water across the bottom in one direction, then across the top in the other direction. You'll need check valves/antisiphon planning on those return outlets if you place them nearer the bottom, but that is no trouble.

You could also leave the outlets where they are and just use pipe to deliver the outflow nearer the bottom.

Finally...go wider than 4" on your overflow boxes. You'll want to able to put some good sized bulkheads in there (1.5"). Also, the more water that your overflows can hold, the quieter you can make them.