If it was a normal egg in the incubator, I would say go ahead and wait till 48 hours or even longer before assisting. But because of this eggs’ unusual circumstances I can understand if you might want to assist a little sooner. If you do assist, just only open up the aircell a little to check for veins. Moisten the membrane, if you see veins, put the egg back and check again in a few hours (but keep making sure the membrane stays moist).
Do you think the egg is on day 27 now?
Do you think the egg is on day 27 now?