With my Berninas, I use the # 37 foot without the flange. I used to use the #57 with the flange, but I guess it's like riding a bike with training wheels. As some point, you just have to take off the training wheels and go for it. With my Singer FWs, I purchased a 1/4" foot (with the flange, unfortunately) and a walking foot at 221Parts.com.
The Bernina #37 foot is 1/4" on each side. One interesting thing I learned is that if you topstitch using the #37 foot, when you line up the outside edge of the fabric with the outside of the foot, you will get a 1/4" topstitch (of course); if you line up the outside edge of the fabric with the first indent on the needle side of the foot, you will get a 1/8" topstitch; and if you line up the outside edge of the fabric with the inside edge of the needle side of the foot, you will get a 1/16" topstitch. I used to hate topstitching (I do a lot of craft sewing, purses, totes, etc.), but now it's a breeze.