I have seen many make it all on their own. Just went toward the wrong end for no apparent reason. So I suggest giving it time to try on its own. And remember, even extra time, since they miss the air cell, the first hours are like the time that normal pippers spend breathing the internal air. They do a lot of absorbing during that time. So chipping them out too soon can be bad. Just watch for the membrane to get brown-ish. Even though we don't see them move a lot, they normally move enough to keep the membrane moist. Paper-white to gray-ish wet is what you want to see. When it gets yellow to brown, they aren't moving enough and the membrane starts drying, and sticks to the feathers.
Big holes vs little holes... I'd rather see them with a nice, open, small hole, with just a beak in it. Big holes tend to let more air in (especially in incubators with fans), and speed up the drying out process. You want them to stay moist and not get stuck. So as long as they have breathing room, a bigger hole doesn't really help.
But, if it starts to dry out, you may have to do the zip, remove the membrane, and let him push himself out.
Curious... Do you incubate with them laying down or upright? I think ones that are laid down tend to be malpo more often, and especially more rounded eggs. But that's just my thinking and wondering.