A word of caution which may no longer be true with new feet.
Several years ago I bought a wider foot for my FW. I pieced squares using both sides of the foot as a guide. They didn't fit and I discovered that the distance from the needle to the left edge was sightly different than the distance from the needle to the right side. So be sure and measure if you switch sides while piecing. one side measured 1/4" and the other side didn't.