Yes I agree it is not perfectly ideal to bore two cylinders a small amount over if it were required. On the other hand it will not affect the power balance enough to worry about in my opinion. I am assuming just slightly larger pistons if possible as I think the pistons are so mallable and flexable compared to the hardness of the sleeves. That is unless he drives it a lot with the present defect. Think of the 3.5 litre with the bending rods. There is only the slightest damage initially but over a long period it gets out of hand. With a little luck all six bores are still good. Replacement sleeves come into play if it is determined the bores are either distorted or massivly chewed out of round or some simular effect.