Looks really nice.
Why did you section off the last chamber? The final chamber where your pump is is where you'll have the water lower as evaporation occurs. Having it that small means that chamber will drop faster. If you have a solid ATO that won't matter though, I guess.
What is the length total dimension?
I might make the skimmer section a little smaller. You don't really need to fit much else in there. No point in having more room in that section then you need. Would use that to make your fuge bigger.
Why did you put slats on the bottom of the inlet chamber instead of letting the water overflow over it. Noise?
is that the normal free sketchup?
Oh, something else to consider.
I have a bubble tower in my sump, just like in your sketchup. I'm now wishing I would've done socks instead and am trying to figure out a way to rig it up without disturbing the system.