Ditto - what lisatodd said.
Also just because your male is smaller does not mean that when bred to your female it will be good for her. You could have a 2.5 male and its litter mate or grandparents could be 6, 7 , 20 , etc.. pounds. You have to know what is behind your dogs, this includes weight. I have seen a female die through labor because they had a larger pup stuck and it caused problems (not one of mine). This is why it is so important to know
everything you can about your dogs, especially before you breed.
T.