I think the eggs really get knocked around during transit and i never expect a 50% hatch. Don't get discouraged, if i get a few good hatches out of shipped eggs...im happy. Even though i spent a few bucks on the eggs, getting one chick was cheaper than buying/shipping the seramas i wanted. It is more difficult to hatch shipped eggs. I Lowerd my expectations on hatches. Now im not so disappointed. I think the best you can do is minimize handling the eggs, keep them small end down...specially during early development, maintain temp/humidity.
I normally do 30% to start but make sure you test your hygrometer. But recently I've needed to hover around 40% due to horrible air cells and I can improve them.
I've never hatched Seramas. It may be a good idea to talk to someone who does it well. There may be some tips.