I love when threads start with 'crazy idea' it certainly will look very odd with the suspended idea but different none the less. I like the porous to cut down on the weigh as well
i have something like this in my 30 gallon. my friend who i bought the tank off of had turtles before. so what he did was he got a plastic rock that was flat on one side, and glued it to the side with silicone. my fish love it.
I know a guy that made a custom back ground with concrete coated syrofom blocks
Only problem is Concrete ***s your water to hell makes salinity goo Off the rocker youd have to cure the concrete for 2 months with a probly a hundred water changes before the concrete gets neutral
Take your tank in your backyard with a bag of quickcrete and some foam and go nuts XD