I think I can say that I'm making progress toward getting to 12 cm. Although I am not there yet, I have decided to take a different tack towards getting there. Instead of going for long distance in lower shoes, I have found that wearing higher shoes for shorter distances has gotten me somewhere. I put on a pair of 10.5 cm pumps yesterday morning and walked a mere 1.6 km, same as I did last week. After about 400 m, I found that I got into a rhythm and they felt much more natural.
After that, I put on these mauve patent 10.5 cm pumps for church, and I wound up wearing them the entire day with no problems. I didn't get a chance to snap my usual picture with the tripod and the remote, so I had my son take this photo in the garage after we came back from grocery shopping. Now I know why I keep the tripod about half a meter tall for taking these shoe photos. You can't really see my shoes when he's standing up full height, can you?