I bench with pinky on the ring. And I MP with my middle finger or ring finger on the ring. I've never tweaked anything *knock on wood*. I lose power very quickly on MP if I move my grip in. Wide grip on bench for reps is not good for your shoulders, its a different story when you're talking about a couple reps here and there, but I would not advise it for rep work.
I've got monkey arms basically (very long lol), so my grip may differ greatly from someone with short arms. The grip I use is comfortable/'safe' for
me.