My tank is the same dimensions as yours 48x24X24. Where I really managed to create more space was by having a custom tank made with an external overflow. Everything is built onto the back of the tank on the outside. Also I tried to use pumps like the vortechs as to take up as little real estate as possible.
As far as the rock work goes I went with very little. One of my pet peves to to see someone with a tank FILLED with LR. I really like to allow the corals to fill in the gaps and leave the fish lots of room to swim at the top.