Sabot is all that you need. It seals the bore on ignition and carries the bullet up the rifling just like the patch does with a round ball. I don't know how you would use a patch with a sabot load. I have heard of people using wads below the sabot and there is a base being sold to make the sabot better for magnum loads but I think that is for very special situations that most would agree is unnecessary. Most sabots now will handle any load that is reasonable.