Looks awesome im getting ready to build one also only mine has a corner overflow. You should put your heater either in the overflow box or down in your sump. Mone has the extra return bulk head also and thats where my heater went. Keeps it out of site.. [emoji16]
I kept it in the tank because it won't fit in my sump properly :-( doesn't bother me too much, but I do plan on getting two neotherms instead in the near future. I just wish I could figure out this pooling of water on my sump... ugh!