Not sure.
For me, the greatest success is determined by:
1. Eggs shipped UPRIGHT
2. FRESH (3 days or younger when shipped )
Yes, of course, freshest is best. Ideally fat end up (I assume that's what you mean by upright?). But, boxes are tossed etc during transport.
Here is a pic of some silkie eggs that are going into lockdown tonight.
More than half were clear at 15 days candeling. I wait for second candle to toss. I finally tossed. There are 7 left, I believe. I ship most of my eggs. But these must be the worst air cells I've ever had. The saddles dip low.