Shoulder injuries on bench are not a result of depth, rather the angle of the humerus in relation to the body. If your humerus is 90 degrees with your rib cage, the shoulder joint is compressed and more prone to injury. For a BB, about 45 degrees is optimal and for most PL's the humerus stays adjacent to the rib cage for minimal strain on the shoulder joint. With that said, I always touch my chest. Touch, never bounce. If you have an injury, then train how you must. But off the chest is the full measure of bench strength. That's why I fucking hate listening to guys talk about how much they bench and then they pull some "elbows at 90" horseshit. Maybe we should only squat to 45 too. My 2c