I started off with a simple 10 gal tank as that is going to be the sump for my 20 gal drop off tank.  

Area #1 is the intake from display tank / protein slimmer. 

Water will flow over a 8" wall with baffles cut in the to the next area. 

Area #2 is the camber for my heater and a media reactor. 

After that the water will flow through mg custom cut out that took me the longest by far lop.  This is to allow a nice calm flow into the refugium area. 

Area #3 is the refugium area

After that the water will flow over another 8" baffle and then down and under the next baffle. 

Area 4 is a bubble trap

Area 5 will be my return pump.

I think I cover everything.  What do you guys think? 

It looks like it's all just press fit in the sump for now but you are planning to weld the joints of the plastic and silicone it all in the sump, Right?

You may want some flow through into the refugium section below your custom evil face cutout so that the flow is from the bottom to the top of the spill over into your bubble trap. Remember that water will take the path of least resistance so you might have adead spot in the far corner of section 3. You could put a powerhead in that section to create some circular flow in that section.

Have you picked out the return pump and made sure it will fit in that section? I'm guessing you will have some kind of auto-topoff and there isn't much room for anything too fancy in that return section for that.

The rest of it looks good and should work well for that drop off tank.