I have a line of cows that have quite a large protruding tailhead, I don't particularly like it, I consider it a fault for prettyness, but they don't have any trouble calving, and make darned good calves, so I'm not going to worry myself about it... The one had a 130 lb calf unassisted (she's about 13-1400 lbs), the other is her daughter of last year who's a spitting image of her mother.. Grandma didn't have a big tailhead, but was about 30" across the hips.. she spat out 140 lb bulls in a couple minutes several times..she was about 1800 lbs when in good flesh.
Another line of cows has a very flat tailhead, it's completely "tucked" into the pins.. they have great calving ease as well, but don't push the envelope on weight like the others seem to do... There's no such thing as a perfect cow... and certainly not for all geographic areas... I do like pretty, but not if it means I have to pull calves... Same goes for high birthweights... as long as they can do it, heck, why not... The 130 lb'er this year is probably close to 500 lbs soon, and he's just turned 3 months.. Perhaps I'll weigh tape him tomorrow if I remember to.