Most of my assists, I think all actually, have been stage by stage, due to the vascular system between the chick and egg still being active at some point in the egg. I've never had a compromised chick. However, I agree, especially with malepositioned that if the vascular system has shut down, (though it's rare that it has for most of us before we start an assist because most people can't wait 24 hours plus) to go ahead and at least do a full zip.
When doing an assisted hatch, it's best to start the assist, go as far as you can, moistening the membranes so that you can see the veining and stopping when you get to an area of veining. Moisten the membranes and replace them for another hour or two before trying again. A good share of the time mine end up finishing the hatch themselves, which is excellent because they get to strengthen those muscles.
It is a hard to descision. I usually assist my malepositions after 18-24 hours. Haven't lost one yet. I agree, many people don't believe in assisting because it causes "weak chicks", but my experience has been just the opposite. Out of the assists that I've done, and there's been a few, I have only lost 1 and that was just over week later because of digestive problems, all the rest have gone on to be healthy very productive members of my flock. People shouldn't write a chick off that needs a little help so quickly.
I think that the chick was malpositioned VeggieMinette. It's legs are in the air cell end whereas the should be the other way around. That would explain such a low external pip in the first place.
With regard to an assisted hatch if you choose to do it, personally I feel that if you do not see excessive blood or what appears to be a "flow" (a dramatic term) of blood, and if the chick is full term, I would attempt to fully hatch the chick. Helping stage by stage otherwise can, in my experience leave a totally compromised chick.
It is a hard call to make. But I know from lots of experience that some assisted chicks do die but thankfully more do go on to thrive and become valuable additions to the flock.
I was slowly removing bits of shell but pulled on the membrane accidentally and it bled a bit at the beginning of my assist. When it had a leg out, I tried to assist by taking away additional bits of the shell. I think it became too exhausted.
I will know what to look out for next time. Unfortunately, for the little one, it wasn't soon enough.
Edited by VeggieMinette - 10/25/15 at 1:15pm