We have found that with heavy arrows and a well tuned bow they fly much the same ..but on border line spine arrows and/or border line tuned bows the addition of the weight of a lighted nock to back of arrow can effect POI greatly
I highly recommend that before you install them and go hunting that you shoot them Prior with your broadheads and hunting set up...even if you had shoot the broodheads before season and the fly dead on.
JMHO
Neil