just a quick suggestion , i built my overflow myself too ( but with pvc pipes ) and to hide its ugly handemade look ( urs s much better lookin than mine ) i built somethin like a box with same size as overflow with black plexi glass and hide the overflow behind it ;)
i used plexi glass to build my overflow box , they r easy to use , come in various colors , and safe .. thought it s better and safer than paint somethin inside the tank .