Instruments
Must say that I would side with SRT on the choice of instruments in a Twotter. Some of the places I've taken them and seen other people take them are not suited to modern Electrics.
It might suit some airline type operations like Merpati, Lesotho in the old days, or even sightseers in the Grand Canyon who most probably have ongoing daily maintanence.
However your average bush operator in Africa, maybe except Zimex, does not have an engineer on sight, let alone an avionics specialist. Day in and day out operating on dusty, bumpy and muddy conditions will take their toll with thje a/c only seeing an engineer maybe once a month.
Add to that, flying tons of maize in leaking bags, (Man, that fine dust gets into everything), high humididty, etc and I figure it wont be too long before you are flying partial panel.
(That all said, I do agree that your average African operator would be unlikely to be able to afford the sticker price of a new one)