Drilling additional small (1/2") holes above the level of the 4 inch holes accomplishes nothing.
Drilling additional small (1/2") holes below the level of the 4 inch holes will allow desaturation of the soil below the level of the drain pipes but only for a few feet radius around the pit. This is optional. A slight hazard exists that mud may enter the pit through these additional holes.
(One morning on WRKO Radio) The tub's not clean! Let's remodel the bathroom.
(One afternoon on WRKO Radio) It's time for an oil change. I'm going to trade in the car for next year's model.