When Yen said her hubby gave up and installed a riser stem, I gave in and did the same.
Result: my back and shoulders are much more comfortable.
Interestingly, the move caused wrist and hand pain, so I tilted the saddle up one notch and it instantly went away.
So after one year, I'm just now feeling like my Buenos Aires is dialed. Whcih is why I've been doing more mountain biking lately. Go figure.