I bought the ballerina dee 2 weeks ago in a size 38; after a single hour of sitting in a car (sitting, not walking) I had developed serious blisters on two toes, & both my ankles; returned it immediately. After heavy brainwashing(!!) by the SA, I sized up to 38.5, & have been singing ever since 
The ballerinas do tend to be narrow.

The ballerinas do tend to be narrow.