play fighting

Question
I got Buddy, a 2 1/2 year old American Stafford about 4 months ago from the shelter, he is an amazing dog, obedient and knows that I am the pack leader.  About a week ago we got another American Stafford, from the shelter, she is about 3 years old and had a litter of puppies about 7 months ago. (Both dogs are neutered/spayed).  They love to play with each other but it seems they get really rough with each other, although neither of them growls or yelps.  They bite each other on the neck (they do not draw blood, I would not allow this), and it seems they both take turns laying on the ground and letting the other hover on top of it.  The issue is this, Missy, the new dog bites Buddy much harder than he does her, and I feel little bumps around his neck, but he is much more gentle with her.  I don't know if this kind of play is normal or should I not let them play like this?  I limit their play time to about 1/2 hour to 1 hour per day and do not allow them to play in the house, when they start to play in the house I immediately put a stop to it.  Thank you for all your help.

Answer
As long as they are taking turns, no one is drawing blood, no one is yelping, and no one is continually obsessively hounding the other (a hounded dog really looks like he/she wants to get away, and when you take the "aggressor" away, the houndee doesn't seek him out again to resume play) then it sounds like normal play to me.  If it bothers you that they are particularly rough or need to tone it down, then you can play fetch with each of them for a while, or go for a long walk before they get to run around and play.  The Bully breeds do tend to like physically rough play, and quite a few of them are noisy when they play, which freaks some people out, but as long as they are not bullying one another, you should be fine.