I weigh all my eggs since a lot of them are dark shelled and it is too hard see air cells. The eggs can be weighed at day 7 and 14 to make sure they are on track for losing 13% The eggs my broody hatched over the summer only lost 7 - 11%, so if it is a little low I'm not going to worry. We also sell eggs to people, so I weigh them before packaging and remove the smaller ones to feed back to the chickens. There are still two pullets that are consistently laying eggs less than 50 grams. 
With my broody there was one egg that had a good sized crack in it. I covered it with fingernail polish. It hatched just fine on day 20. Beautiful pullet that I sold to my neighbor.

With my broody there was one egg that had a good sized crack in it. I covered it with fingernail polish. It hatched just fine on day 20. Beautiful pullet that I sold to my neighbor.