Stumbled across this (as am not a modeler) but seeing the trouble you guys go to to get it perfect, thought I could help.
These detailed pictures will show you exactly how SAAF Harvards looked in the flesh. These photographs taken by me from flying in "Old Nelson" #7111 in 1987. You can see some fine detail on the markings and instructional labels on the aircraft. You can also see the exact detail of the canopy.
Note, unlike this one, some of the models I see have very vivid dayglo, but in reality it faded, almost giving it slighty yellow appearances from certain angles. Also the yellow of the numbers is much yellower than the decals I see. You can particularly see this dayglo in the second pic which is 7111's wing. Taken on the way to a Air Combat Maneovers exercise out of Donnotar Central Flying School in South Africa, where all 'pupil pilots' trained for service in the SAAF.
Pity none of your models have the CFS Africa/Eagle Sqn badge on them. You could make these by copying from a book (like the SAAF at War), photoshopping them to the right size and printing them on decal paper.
Have pics of Impala's and the Silver Falcon aircraft too.
See how the dayglo looked faded on the wing below....