Were there many Westerners involved in the fit test, Paul? Chatting with some headfi buddies in Asia, I've found that we find different IEM shells fit us quite differently. This is across multiple people.
There were people from Europe, the US and China with a few other countries. Both men and women were tested. Different sized of ears and shapes and we had no fit problems. The shape we use was derived from the study of the ear and many fittings.