I'm with the boys from AZ... once it starts to hurt (and not that good kind of hurt) I'm putting you on "time-out".
I don't buy the "carried away" bit though. I don't care what you say, you're always in control and aware of what's going on. So that sounds like a cop-out to me.
I'd definitely talk to him about it, beforehand - and STOP him during sex if he starts to do it again. Maybe not abruptly the first time, but try to ease him into a different way of doing things.
Better yet, why don't YOU take control of things. I'm assuming that you'd be the bottom in this scenario. I've rarely heard of a top complaining about aggressiveness
. So if that's the case, I'd change things up so that you're on top and controlling how fast/hard things are going.
And if all that fails..... do like with any other dog and get a water bottle and spray him when he's being bad.