Same widths

I want to create a stylistic set with the same character widths as the original characters. And when I change the width of a character the width of the character in the stylistic set should change in the same way.
I tried to reach this by defining the width in the stylistic set by the character name (width of a.ss01 = a), but that doesn’t work. What’s the solution for this problem?

Such metric keys only work with sidebearings, not widths.

You could do it with a small Python script though:

Thanks, I am going to try the Python solution.