In most cases, with the same person shooting the bow, if a nock height set for three under, assuming the arrow flight is good, it will work fine for shooting split finger. Each archer puts a different angle on the string when they draw, so a nock height set for one person may or may not work for another. On the majority of bows I have shot, a nock height of 5/8" to 3/4" above the shelf works best for three under, about a 1/8" less for split.