Fergus's play style -what do you think?

4 month old GSD, quite a confident little sucker.  Playing with a female BC mix, about 8 mos, same size (which is yikes, right?  He's gonna be HUGE).
 
Jaw jousting, F. gets noisy, dogs take a break.  Tails down all around.
 
BC mix goes belly up, F. stands over her, she is between his feet, firmly underneath him.  He stares, starts getting a little growly.  She does not try to get away, expression still soft.  Tails still fully down.  Dogs take a break.
 
F. gets a little more pushy and starts vocalizing.  BC gets up and continues playing, but F. escalates a bit to some body checking and quite loud vocalizing.  BC tail in neutral position, F.'s tail still fully down.  Humans step in to break it up.  F. tries to "push it" a little more with BC, but is easily called off by humans.  During the whole thing, no tails ever go up.  BC never seems concerned and did not act stressed, as far as I could tell.
 
What do you think regarding play style?  F. is very opportunistic.  If a dog gives an inch, he will take a mile.  On the plus side, he is easily redirected or called off, and also respects corrections from other dogs, i.e. the 150-lb. mastiff who told him to "stop it" in a very appropriate way and thus experienced no more pesky advances from Mr. F.     I'm not concerned, just looking for insight.  I haven't been around such a confident, stable dog like this on a regular basis for a long time, so I'm learning too!
 
I really need to get video...