Not trying to put in your business about what you breed to, but we just had a heatwave heifer try and drop a balboa calf (unfortunately the calf didn't come with two feet forward and we were late catching it), but she did have a 99 lb dead heifer calf. By no means small, but it was shaped right thank god. The vet who came out said she had plenty of room to pop her out herself if the legs had been properly positioned, unfortunately the calf didn't make it due to the lateness of getting to it (and we couldn't get her pushed back in to pull a leg up), but fortunately my cow did make it and the calf was pulled in the position of one foot forward and one back with a calf jack. The cow never went down during the pull and she was tied to a panel with the halter, and aside from some little more than average tearing, she was fine, but again it was a 99 pound calf for a first time heifer, not my idea of a low birth weight. My only good thing was at least I know my girl can handle 99 lbs as long as the calf is shaped right. She walked a lil stiff for a couple days but all is well now. I don't think Rocky is a good choice for a heatwave 1st time calf and I definitely will not do it again. Just sharing my experience.