Thanks for the explanation. CO2 on a closed loop sounds like a great idea.
I like the idea of the peninsula overflow, actually moved my HOB oveflow to the right hand side of the 100 gallon tank after I took my black background off. Then no equipment showed on the face of the tank save for the small skimmer box which your external overflow doesn't even have!!!
My daughter was wondering how you are keeping critters out of the sump.
Hope your rocks come soon so you can plan something amazing to put in the tank to go with that terrific wood.