Here's a hint, there is a very good reason why nobody uses a shotgun with slugs in Africa. While that massive three quarter inch bore is impressive to the eye, slugs don't have what it takes for deep penetration on heavy game. There is no magic.
There's a reason why big, dangerous critters are stopped by big, heavy rifles and not shotguns. There's a reason why they use .375's, .450/.400's, .416's, .404's, .458's, .470's and .500's. Not only do those cartridges utilize large diameter bullets but they are also heavy for their caliber. Yes, a slug will stomp a deer pretty good but they lack the sectional density that is usually required for deep penetration on heavy game. People seem to freak out when I bring up sectional density, as if I'm trying to fool them with a magic trick but SD is simply the easiest way to compare heavy bullets to one another. It is very well proven what cartridges work best on the heaviest of game. The one thing they all have in common is that they use toughly constructed, large diameter bullets but that isn't enough. They must also be heavy for their diameter and the number we use to determine that is sectional density. I'm sorry but it is not an earth shattering revelation that a shotgun slug with a sectional density from .117 (1oz Foster) to a best of .233 (Dixie Terminator) is not going to penetrate as well as a .450/.400 slinging a 400gr with an SD of .338, the .416Rigby slinging a 400gr with an SD of .330 or a .458 slinging a 500gr with an SD of .350.
In penetration testing, shotgun slugs penetrate how we should expect them to. Comparable to handgun bullets of comparable SD and velocity. They just make a bigger hole.