Hi rookhawk,
I've not been to Africa very many times, so I am still learning.
However, I have had the great privilege of firing 6 rifles total, belonging to 3 separate PH's (.222 Sako, 7x57 Zastava, .30-06 Brno 600, .30-06 CZ 550FS, .375 H&H Brno 602 and 458 3" S.A. Express CZ 550 Magnum).
Half were only at paper targets but I have used the two .30-06's plus the .375 mentioned, to cull with and take a couple of sport hunted antelopes with as well, on different trips to the same camp.
All 6 of these rifles were in tip-top shape, except for bluing wear on a couple of them, from carrying many a long mile.
Mechanically they all 6 functioned right, crisp triggers, etc., and all were accurate.
The .458 had only express sights but the others wore either a Leupold or Zeiss scope, (except the .222 which wore a "Lynx" brand 4x scope).
The Lynx seemed like a middle of the road to slightly less than perfect quality scope, but at the least it was very accurate anyway.
Maybe aside from that one scope, all the above were such that I would happily bring any of them to Africa if they were mine, (the .222 caliber might be fun to hunt "the tiny ten" with, not to mention hunting jackals by means of a rabbit squealer call).
Those three PHs are the "real deal", and not very likely to own anything less than a well tuned firearm.
I would have no worries if any of them were backing me on any DG species, (including the most dangerous ones - human criminals).
Personally, I would be nervous (very nervous) about hunting dangerous animals with a PH who could not be bothered to maintain his rifle/s.
I once refused to get in an air taxi here in Alaska, because when the pilot finally showed up and drove us from the hotel out to his tie-down, he said "that damn tire is flat again, well ... I'll have to see if I can borrow a compressor to fill it and then we can go plus, I forgot to bring some oil anyway so, I'll be back in a few minutes".
Also, I noticed dirty black oil dripping (one drop about every 3 to 5 seconds) from the bottom of the cowling, into an impressive oil puddle, on the ground and large lengthways black streaks under said cowling, obviously from flying it that way.
As for unprepared or generally incompetent clients who might want to rent a double rifle, as opposed to renting a Mauser or even bringing their own rifle of any description, I am of the opinion that those types will always be an unprepared nitwit which their unfortunate PH will be stuck with, always having to keep one eye on the fumbling client and one eye on the game.
For guys like you and I renting a double rifle - We would if nothing else buy a less than fancy double shotgun with double triggers, a case of slugs and practice our boodies off.
The shrugger and the nitwit would not practice very much with anything, even if they already owned it.
I only have one double rifle but cannot afford to return to Africa with it at the moment.
Suddenly being able to borrow or even rent a double over there has huge appeal to me, because although heart breaking, I could sell my double and use the money to return to you-know-where for another safari.
Being able to use that vintage .404 Mauser is likewise very tempting.
It is tempting.
Well anyway cheerio,
Velo Dog.