What do you think of this one?
SFO-PVG-SIN-SYD-JNB-FRA-ORD
GCM claims 29,000 on the nose. *A RTW tool says 28,979. Then, we just need to get from ORD to SFO.
Replacing the end of the trip with JNB-GRU-IAD-JFK comes in at 28,836 (though I hate leaving those 164 miles on the table) and lets us fly p.s. back home. It would also give us three continents I've never been to (leaving only Antarctica).