I sent some eggs to sandspoultry this spring. I sent sixteen regular sized eggs and just crammed as many pullet eggs in there as I had on hand, just cuz. I wanted to throw every egg I had his way for a good hatch. I thought the pullet eggs would be a bust, but hey, every egg is a chance... Well, he told me that the pullet eggs hatched the best of all. So go figure...
I have had good luck under silkies. Under silkies however, I have also had them pip the wrong end and drown. I think marans can't find their way out of a paper sack, to tell you the truth... at least a too high percentage of them. At home, with non-shipped eggs, sometimes I will only get 60% hatches, but that is in a Hovabator still air with a turner. Under broodies usually much better.