If you're seeing no change in the point of impact with changes in arrow spine, then you are probably shooting to the left because of form problems. Shooting to the left, for a RH shooter, can be caused by many factors:
1. Torqueing the bow, either by grip pressure, often with the thumb, or by torqueing pressure to the string, by not having the fingers pulling parallel to the string. The primary cause of string torque is a tense forearm. If you are pulling with your back muscles, you should be able to relax your forearm, and feel a stretching sensation in the joints of your hand and fingers. If nothing else, try alligning your fingers parallel to the string, but this is not as good as relaxing your hand and fingers, and letting the allignment take care of itself. If you relax your bow hand at full draw, and the bow wants to change its angle of cant, then you're torqueing the bow and/or bowstring.
2. Not coming to full draw, such that your string forearm is in line with the arrow, viewed from above. When your string forearm is at an angle to the arrow, viewed from above, the arrow will tend to go in the direction of your string forearm.
3. Not having your shoulders perpendicular to the target. The arrow will tend to go in the direction your shoulders are pointing.
4. Not keeping a slight bend in your bow arm. Shooting with a straight bow arm tends to encourage the arrow to go to the left. Some people disagree with this conclusion, but most people agree with 1-3.