I never pre-mount. Always shoot from low gun. When I try a gun for fit then I look for pull length, cast off, pitch and how my eye aligns with the rib. If it fits, I no longer worry about the rib/bead. To some extent, fit may be adjusted by placement of my leading hand. (Especially when changing from mild weather to winter shooting with al the extra clothing) Once it's good it's good. After that I really try to be concentrating the target not aiming down the rib. Times when a quick snap shot presents itself, a crushing hit is a bit of a surprise. No conscious thought at all just mount, track and pull. Bit of Zen and shooting and do wish I could do that all the time.
