Controls the amount of seam allowance on flat-felled seams.

The armhole and side seams on the shirt are flat-felled seams, and those require extra seam allowance. How much is a matter of personal preference, since some people prefer wider flat-felled seams, while others have a preference for more narrow flat-felled seams.

This option controls the amount of flat-felled seam allowance as a factor of the regular seam allowance.


## Efecto de esta opción en el patrón
![Esta imagen muestra el efecto de esta opción superponiendo varias variantes que tienen un valor diferente para esta opción](simon_ffsa_sample.svg "Efecto de esta opción en el patrón")