Like most things I tend not to be a purist. A good shooting stance will naturally align the weapon with the target. Expedite your recovery and place follow up shots on the target/attacker.
Work with the pure stances, adapt them until you find the one which allows you to accomplish your shooting objectives.
Once you get your trigger control, breathing and site picture down, then follow Kraigways advice and practice shooting from a variety of unorthodox positions and light levels.