The good thing about a step retard is you can set it up to the level you want. You can set it up to be aggressive or conservative. My numbers were just an example. If you wanted you could use 0.5 per psi from 0-3 psi, 0.75 from 4-8 psi, and 1 per psi from 9-10. 1 degree per psi is fine too but a lot of people will tell you that is it very very conservative. I only suggested a step retard because it will improve your low boost performance.