Pilots in SAA are well trained and extremely well paid by international standards. Someone once said over paid actually.
Cabin crew, well, do familiarize yourself with the safety card in the seat pocket and don't expect anything other than the most perfunctory service. Anything else would be a bonus. Someone said that was a generalization of course.
The approximate position of the ITCZ can be gauged before departure by reference to this link.
The ITCZ in Africa
Keep your seat belt loosely fastened at all time, be aware of the position of the nearest sick bag and you will be fine.
By the way, chop at altitude tends to be caused by a jet stream. The ITCZ can produce movements more akin to bull riding at Madison Square Gardens.
Don't forget that the wing of a 747 can move twenty seven feet in the vertical plane at the tip before structural damage limitations are exceeded. Obviously the arc of movement is greater down than up. At twenty nine feet of arc the wing breaks off. That's a lot of safety margin.
Edit to add that I fly a lot between Amsterdam and Johannesburg and that I can do it myself.