reseeding pasture

I want to reseed our pastures using a set of 4′ cutaway discs with two gangs. We have had good results with an 8′ tractor pulled set. It smooths out the fields, a lot of which were old potato fields that had never been replanted as pasture and still have the rows of potato hills. Also there are relatively few rocks brought up to the surface with the shallow working depth of the harrows. The sod is not tough and breaks up to a fine planting medium.
So I am wondering if my team of oxen are up to the job of pulling the 4′ set. They weigh 2600lbs together. The manufacturer recommends a 15hp tractor with the set.
Any opinion on this technique? Or any ideas of alternative shallow tillage reseeding?