I happened to randomly open African Rifles and Cartridges - as I often do - to a page on rifle carrying.
As John Taylor mentions, the "African carry" is most useful when you have a bearer in front of you and you are not carrying a rifle at the time. In this way, you have only to reach forward to slide the rifle from the bearers shoulder and you are ready to go. In fact, he also states that he has no sling at all on his rifles. I can attest that when carrying a double in the Colorado mountains, I found myself reverting to carrying my double in one hand just at the balance point.
As for safety, the usual rules always apply - don't allow your gun to point at ANYTHING you are not willing to destroy.
9ThreeXFifty7 is right on. I grew up with seven older brothers and plenty of "dangerous" environments. Firearms never took part in a single injury in my family. Excluding mental anguish of course.