Having recently experienced a 28 degree departure from FAJS ( a mild, early Summers day) in the A340-300 (CX) I would have to say that SAA have bought themselves (in the -300) a whole lot of problems.
The MTOW (structural) of the 340-300 is 275 000 kg.
We left at 251 000 (performance limited) using every trick in the book.
Full pax, their bags (I presume), no gas for Mummy and about 20 000 kg of "high priority" cargo on the ramp (seafood).
The take-off performance was marginal, we never made the 8000' restriction (not even close) and to say I saw the whites of some pedestrians eyes as we crossed the fence is not an exaggeration.
We have been told the -600 is a different airplane completely, nowhere near as limited. After an LAX next month, I hope to be able to corroborate that statement.