I read the thread at Flypast and I admit I'm still skeptical as I've never seen that color combo with those roundels, but Peter Arnold is the man when it comes to Spits and some of the others discussing the scheme are good Spit experts too.
I think the consensus seems to be that the Land Temperate scheme was in use in the MTO (I must admit I've never come across it, but that doesn't mean much)
It also seems clear that most don't believe the 45 upper wing roundel was in place so in that regard the restored Spit has it wrong, but other wise it's a different scheme for an IX with the green brown and azure blue undersurfaces.
I believe they still had the yellow ID stripe on the leading edge of the wing too, unlike the restored Spit in the image.
I'd do it on the AH IX if you choose to do it though. Full span wings and small tail on those SAAF birds it appears. The AH IX is a good performer down low too so I'd take it up since I'm avoiding the XVI these days

I e-mailed Peter Arnold to see if he can confirm any of this and point to any photos of the actual aircraft, instead of the restored bird.
Gotta love that IX