Pretty tight work so far, and I really get that feeling of suffering to come with the female's pose.
The one thing that does bother me is the centuar's legs. One, the feel short for his body and head size, and two the way he's resting is not a natural pose for a horse be in, and that makes a bit awkward feeling for me.
I'd say twist his back half a little, so the hindleg is a bit more spread out to the side, and the hindleg on the other side is underneith his body. That would also mimic the twist to the female's body and unitfy the poses of the two more, while making it a bit more natural looking.