Kyle, the biggest problem with turning a tank that isn't drilled into a tank with a sump is in the overflow. A drilled tank's overflow is going to allow water to return to the sump using gravity, while a undrilled tank is going to have to return water to the sump by siphon. Now, if the siphon is broken for any reason, then you a pump in the sump that is returning water to the display, but the water that is going to the display is not being returned to the sump. Within a minute the tank is going to overflow and the water in the sump will be put into the display. There are ways that a siphon can be restored automatically if broken, but that usually means more money.