If the point/goal is to fine tune the dish, I do this off either 99c or 103c, since these are the narrower beams, so I find the center of them easier.
Doing this, has the 101 also in its center, which might be more centered than trying to do it off the 101, because it's a wider beam.
Doing this, has the 101 also in its center, which might be more centered than trying to do it off the 101, because it's a wider beam.