Although I empathise with "analogphoto" & his position, travelling around Africa on airlines with Camera Bags is a bit Par for the Course, it's not an unusual situation, as pointed out in an earlier post, most "Tourists" go there for the Wildlife & Photography generally goes with that pursuit.
Insurance is a total must, your just risking everything by taking the chance that you will be allowed to comply with the carry on regulations, and that's just simply not the case with SAA, I have been on numerous flights where the Cabin Staff standby at the Door while boarding (or in the waiting room) & simply designate what carry on gear will be tagged & taken to the hold, and call me a cynic if you like (been called much worse), but the Cage full of chickens never gets tagged, the Bag full of Papayas never gets tagged, the Huge Box full of Donuts never gets tagged, it's always the large Camera Bags & the Hard Cases that are likely to have valuable items as carry on, this is what gets tagged and the Cabin Staff generally don't care if your flying Business Class or Economy, wether you are complying and under the regulation weight or not, it's basically a lottery.
Having the Camera style waist coat with a couple large pockets is just good sense in the event you are forced to remove some of the more valuable items for safety, and if your sitting next to "analogphoto" and a long pointy object extending from your clothing pokes him in the ribs (we will assume this is a 70-200f/2.8
) a nicely worded apology and explanation should suffice, it seems to with most reasonable minded people.
In any case, enjoy your trip & take loads of wonderful Images, but while in Africa try to keep in mind a comment made to me by a South African friend that won the Wildlife Photographer of the Year competition in 2013, "In Africa, Crime does Pay".
Arranging an extra seat as has been mentioned is a good policy, I always do this for the flights between the airport & the Camps as the smaller Cesna type flights are quite restrictive on Bag weight, generally 18-22Kilos all in, so an extra seat is almost a must in my case, but, the major airlines flying main airport to main airport, generally don't allow you to buy an extra seat in your name, SAA are one of these airlines, you might consider Flying Business Class if it's an option as you get an extra few Kilos of Carry on allowance.
Try to keep within the Regulation carry on requirements for your Class of Seat
Steer clear if possible regards Hard Case Carry Ons (I don't mean "analogphoto")
Get yourself a good large pocket Camera Vest, just in case
Prepare yourself to be calm & smile a lot, may not help but will make you feel better
Absolutely have Full Insurance Cover on your Equipment
Prepare for the worst hope for the best
Always remember, Crime does Pay in Africa, but with suitable precautions it's a remarkably Beautiful place.