Scott,
Looks like you've done a lot more hunting than I have - (I'd say 99% of this forum has).
But -
This question came up on my last hunt - 416 Rigby.
Like you, I have a 375 H&H and a 458 Lott, I also have a 450/400 Double with a 500NE Double on the way.
Where does the 416 fit in this line up? Does it take the place of the 375 or the 458?
When and how would you use it?
Don't take this the wrong way - I'm all for buying another rifle.
It's similar to the shoes thing with my wife, "Why do you need so many shoes?" Answer - they all have a specific application.
The other question then becomes, which do you take? Now you have to get them and enough ammo into Africa.
I suspect ballistics would be a major factor - not something I am very familiar with.
Please share your thoughts