Glad to hear the tank is on the way!
I find Del's don't get nearly enough love... Everybody wants to go Endli because they're a little bigger or ornates etc. But I think your original plan of a pile of Del's and Bushfish would make for an awesome tank.
As far as CB Del's size yeah most of them may end up around 10-11", but I had one in college that grew to a true 14.5" (nearly 37cm) - wish I'd been able to keep that fish between moves. He was a beast