I would sooner recommend that the egg with the detatched air cell be placed in a cut down egg carton and allowed to hatch upright. This will theoreticall keep the air cell up and better stabilized it in the general area it needs to be. People do things differently and have different methods and that's great. Personally I am not an advocate for going into an unpipped shell. The only safe place before a pip to enter an unpipped shell is the air cell and putting a hole in the air cell of the egg is going to do absolutely no good if the chick doesn't pip through the membrane into the air cell to begin with and that's what the trouble with detatched air cells is wether the are going to be able to pip into the air cell. You can put a hole in it, but if the chick doesn't pip into that area, that hole is going to do nothing. If the chick pips into the air cell, then you really don't need the hole cause he's doing what he should and if the air cell is big enough he shouldn't needed added air before making the external pip. If the air cell is small to begin with, that's another good reason to hatch that egg upright, to cut down on the chances of aspirating on excess moisture entering the pip hole. I, personally, would only consider making a pip hole in the air cell if the chick has internally pipped into the air cell and the air cell is extremely small and doubtful that it will provide enough air until the external pip.
It's iffy. What kind of bator do you have?
Were you able to get a pic?
