I can never find it but there's a great website that shows why crotch danglers are bad, more so for the spine than the hips.
Even with good carriers like Becos and Ergos it isn't recommended to outward-face carry very often or for very long. It's hard on baby's back and on the person carrying the baby because the weight of the baby isn't leaning naturally against the parent's body. I'll see if I can find the link, but basically that's my rambling summation.