What I use is pretty similar in trajectory to your idea as I'm shooting 300gr round nose, mine is a .375 H&H Merkel 140AE double, here's a reachy shot with it just a few weeks ago on Gemsbok / Oryx. As long as you're well practiced and know your rifle, there is absolutely no reason why I wouldn't see a 9.3x74R double as perfect for what you're setting out to do. It'll add some class and enjoyment to your hunt too, no doubt. I've hunted the Limpopo as well and as others mentioned it is typically inside 200 yard shots.

2 minute video of the Oryx shot with the Merkel double:

https://www.youtube.com/watch?v=tWaZk1MGPuY