There is something like a recommended weight for hatching eggs for every breed in the Standard. Bielefelders should be over 60g. Yes, size matters. ;-)
I second this! With the exception of my bantams, I simply won't hatch eggs under 1.8 ounces/ 51 grams. I've found that chicks from these larger eggs simply thrive better and prove so much healthier. Plus I get a better hatch rate.