Well do an experiment, hold a 5/8,s razor two pine widths off of a flat surface then measure the angle, then do the same with a 8/8. Se if the angle is the same at two spine widths, but in reality, that's just a starting point usually just lay the blade flat on your face and start raising it till you get good cutting with out scraping. Plus different areas of your face will be different angles of attack. This the reason this way of shaving takes months to learn well.
Tc