Can't remember if I posted it here or not, but when I set my Biele eggs Tuesday morning I made a little cradle to hold the worst air celled egg upright (with a balancing egg from my flock on the opposite side) in my horizontal turner bator.
Out of curiosity, last night I took a tiny not so bright flashlight and tried to peek into the eggs while they stayed in the bator. All I did was remove the lid and shine it down on the 2 upright eggs and a few that are on their sides.
The darker upright egg that was saddled the worst looked interesting. The air pocket side that was halfway down the shell had come up to the top, but was totally jiggy and loose on that side. I could not tell if there was any development yet, too dark to see beyond the air cell. My own blue egg was fine though the yolk was near the top, not in the middle. Don't know what that means, if anything.
I tried to peek into a few eggs on their sides with my dull light and think (??

??) I might have seen some light veining. that was last night and today is just now going on day three.
If I can behave myself I won't do a full candle until day 7, but might recheck the upright egg in the same manner to see what the air cell does and if it can be put on it's side.
For now I'm gently twisting the 2 upright eggs 5 to 7 times a day.