Tank Redesign

[seymour47]

I'm currently designing some additions to an 11+ gallon tank I acquired recently. I'd like to add three chambers onto the back; an overflow/skimmer chamber (left), a multipurpose chamber for a fuge, chaeto, filter material, heater, etc. (middle), and a return pump chamber (right). Any advice or suggestions of what I have wrong on the design would be appreciated. Thanks.