I used to do the same thing.. my partner kept telling me im gonna drop it on my self so I just started wrapping my thumb around.. when you do that you ahve to tilt the top of your hand back to be able to hold the bar.. I wonder if this is hard on the wrist?
you don't HAVE to tilt your hand back....after i broke my arm and wrist during football, and played in the cast, i developed bad tendinitis and inflexibility. I did bench for a very long time with my hands and forearms lined up, not perpendicular to each other. Of course, you can't lift as much weight this way, but you can still develop good pectoral muscles. If strength is your goal, you gotta nail the PL-ing bench form.