She is officially on her way out. The crack is now becoming a hole. I've heard the struggle of hatching is important for the chick to build strength. It makes sense. I am usually of the mind don't interfere if you don't have to. I just had a Silverudd pip upside down though. I flipped her and put her back in the incubator. I watched and I did see her beak pushing at the membrane so I think she'll be ok too. So 6 officially pipping externally..
Sounds like the hatch is moving along nicely for you! Do be careful about opening the incubator while you have external pips. It's good to keep it closed to keep the humidity more consistent now that the membrane is exposed.