Yes. I made my returns out of PVC
pipe but the concept is just like the picture. One thing to do is to drill small holes in the pipes just below the water line in the display tank. When the pump stops like in a power out the small hole breaks the siphone and you won't drain your dt into the sump. Also don't fill the sump too full until you make sure it can handle what will get sucked down if the return fails.
As for how you have it set up is your call ( what's in the sump.). I have my drain from the dt and skimmer in the first section, rubble live rock chaeto and heaters in the second and the last is the return pump and area for my temp and ph probe.
Some people do sand beds in sumps some dont. It's all up to you. You don't even need to make chambers if you don't want to especially with a hob
skimmer. The only reason you might is if you get a lot of bubbles from your drain tube or skimmer then filter socks can minimize this so your return pump wot by suck them into the dt.
I agree that if you properly brace the filled dt you can probably remove the center brace to get a 20l. I had to do that to mine to get a 20l in my stand.