How are you keeping the nocking point consistent? Brass nock? Tie-in nock? I know it's probably heresy but anyone try shooting with a release?
In Korean trad, the nocking point is typically found by balancing the bow on the edge of one's hand (usually at the bottom of the center serving) and then flattening the hand up the serving; where your pinky finger is is usually where the nocking point will be. Of course, hand sizes vary and such, but that is the traditional way. As for a nocking point, sometimes it will just be marked on with a permanent marker. If the serving is too thin for the arrow nock, serving string or even floss is often wrapped around to make a nocking point.