Bottom line
If you use a medium bore, make sure that you are a surgeon with it. If not, you might find yourself praying for something bigger.But, then again, I have seen guys so afraid of their big stoppers that they would be better armed with a base ball bat. And it is not true that you will 'forget' about the recoil in a stressful situation.

We use light loads for training rangers, it improves muscle memory better when you do not fear the rifle. When the tsama hits the mopani tree, they should theoretically have enough muscle memory (read reflex reaction to the charge), training, and guts to face what is coming.
Been there, done that

Groetnis
Andre