shipped eggs are VERY hard. if you get 50% hatch rate you are doing extremely well. 6/18 isn't really that horrible for shipped eggs. Sometimes the PO is not very nice to them or just bouncing in a truck can do damage that you can't see. I wouldn't worry too much about the saddled air cells. I had some that were EXTREMELY saddled and they hatched fine and are now 5 mo and 6 mo old all doing great (2 different hatches and all shipped eggs). Just mark where the air cell is so you can tell if it pips in the air cell or not that way you have an idea of how long you should wait for them to hatch with out helping. Most of mine pipped in the air cell and hatched with in the 24 hrs. a few pipped on the wrong end or outside of the air cell and took longer to hatch (since pipping not in the air cell is like an internal and external pip in one).
GOOD LUCK!!!!!!!! Can't wait to see how your hatch goes!