No you cannot. I signaled my intentions by supporting neighbours from the very first move, but the divided nation of SA cannot support itself - you simply cannot get enough reinforcements down to protect either the South African part or the Antarctic part. Worse still, you are sitting next to Kenya which has arguably the best starting position of all - a complex mix, but with SA being so piss poor weak and Kenya being able to both feed again and again on the African continent and also keep launching fleets so easily and into such rich waters - it is a stand out to progress.
What this means is that even though I support FA to move quickly to take extra territories down south and show friendship, he still wipes me out and there is nothing I can do - I cannot have more than two units there in time and I block the SC with any defence; and even though I signal to Kenya by supporting him as well - he just doesn't stop and rolls straight over me. Again, I cannot get the builds. Worse still, with only two home SCs in Africa anyway, you end up having to block at least one of them in order to mount even a half-hearted defence.
If you get one build (if!), do you plonk that on the ice of Antarctica to try the futile exercise of holding your single SC there? If you place that unit (if you can) on the mainland of Africa instead, the Antarctic is the proverbial dead duck in less than it takes to shoot a penguin.
SA is a total joke in gunboat. Simple.