The only thing is you will reduce the cup size by 2 row . In this tutorial, the dimond shape of the cup for S size is a total of 30 rows (12 increseanglly ,6 middle ,12 decreasinglly ) , So for XS you do 11 increasinglly ,6 for the middle and 11 decreasinglly , total 28 row . For the upper part of the cup, you can do 8 or 9 rows .