I've seen one of my toms do that. I thought he was doing it wrong cause our other tom was a giant white and he would try to mate but it looked more like chicken mating since he didn't stand on her but must of been cause of him being overweight. The other tom of the two we have now is bigger (blue slate) and he usually runs over and tries to push the other off and earlier today the hen was kind of trapped under a brush so she couldn't get out of the way in time before the other tom stepped on her also. Luckily she got away cause I couldn't get the gate open. I've seen her limp a couple of times but usually after an hour she is back to normal. We have two other females but they aren't overweight so I never see them mate.
