then your overflow box only needs to be 6 or 8 inches down from the top of your tank as opposed to the other needs to go all the way to the bottom of the tank, leaving you extra space below the box... but you would need extra space behind the tank for plumbing as it now goes behind the tank instead of under..
your drawing makes sense but, what I can't wrap my head around is how does the water get from the tank into the overflow.. is the tank drilled and what kind of screen or whatever is over the hole.. sorry for sounding stupid, I don't do anything until I understand it 100%..
the other is a little more tricky.. they do make a product to make it simple.. they call it a ghost overflow...you would still use holes through the back..
I just think its a much cleaner look and allows you to have easy access to the plumbing if need be and if any thing leaks its directly over the sump. But it does take up in tank space if that's a worry, but not much will flourish under the overflow box I assume.
When I drilled my 200 I did it like the original Bean like in Dale's first pic.
If I were to do it today I would definitely do it like the second pic with a ghost overflow (thin panel with the weir in the tank covering the holes Heath) leading to an external box.
BTW...if you are using a wavebox a center overflow will let you build a bigger wave. A corner overflow will be better if you use a Herbie drain system (2 drains) center overflows look better if you need to go wider to do a Bean with three drains.
Those ghost overflows are the way to go if you have no worry about money. Sometimes I dream about being an acrylic overflow box builder and raking in the cheese.
Well not as much as I dream about selling coconut monkeys on the beach in Kailua