I wanted to use the electrical box as a floor too but I used it for a floor for the park before it n before I knew it my terrain was up, so big kudos for that.
I am seriously re-considering doing this park again in a new location. . . I did get the roof on before, I used the same piece as you too, the maloof wall? . . . but didn't have enough terrain to make it look mounted plus u could see the banner from the stadium wizzing around below it, looked odd.

wish could sesh this version though, does look good.