A fixed 8 Power on a .458!!!
I urge you to spend a little time behind the butt of a forty class gun at a range before investing in the theoretical. To paraphrase a fellow contributor whom I appreciate immensely, you can load that thing with a frozen herring and you won't need more than 4-power. And a fixed 8, regardless of manufacturer, is about as bad a choice for hunting Africa (or most anywhere I have ever hunted) that I could imagine. More importantly, all this theoretical two scope stuff set up for two loads tends to fall apart in the bush. You are drifting along behind your trusty PH and tracker two hours into trying to walk down a dugga boy. A beautiful kudu, zebra, bushbuck, whatever freezes at 175 meters. It is getting late to continue the buffalo approach and the alternative animal is about to bolt. Is anyone really going to change scopes and ammunition? And the truth is, a low magnification scope will make that shot much easier, just as accurately, and much, much quicker than searching for him with an 8-power.
If you really want to try and turn a Lott into a PG rifle with a light bullet, and the group difference is significant at 100 meters, then just tape the click difference to the side of the stock (or memorize it). Whatever scope you are using for DG will be adequate for any other game you will shoot at to include a duiker, and turning the top turret a few clicks is much simpler than trying to change scopes.