Bare shafts are more apt to show errors in tuning as well as form. Fletched arrows provide stability to the back of the arrow and provide more error support in tuning.
Best thing to do is shoot at 20 yards, anything closer and the arrow has not properly come out of paradox before it strikes the target. If the arrow is hitting nock left, that indicates a weak spine, nock right indicates a stiff spine.
So if you are hitting nock left (weak spine), lower your tip weight, or go with a stiffer spined arrow. If you are nock right (stiff spine) go with a heavier tip or weaker spined arrow.
What's getting me is a nock left arrow should be hitting right of where you're looking as the arrow flies in the direction of where the point is (point hits right in nock left). This suggests either you are shooting too close and the arrow cannot completely come out of paradox, or an error in your form, or you (like me) tend to move your bow arm upon release.