To be fair, your local also has a huge overseas component - so it's more like 75/25 - which is a good thing. Overseas, a 4% draw down (and upped every year by inflation) is recommended - as in, in almost all scenarios, the person never runs out of money. The further you push it, the more likely you might run into problems. 5% is not too far out, but tweaking the budget might be worth it for the first few years and see how it goes.
Also, of course, look at being tax efficient.
Might be worth putting R500k in a couple of high yielding property REITS - some paying 12-16% - (TEX, DLT, TWR) - might get you close to 5%
4 % on 5mill and 12% on 500K gets to R260K vs R275. That said, the full amount gets added to income vs capital gains rules for the rest so might not be as attractive depending on your tax situation.