My vote goes to the Guidelines 4 Quilting Prep tool. Looks pretty useless, but will assure you of the correct seam allowance with any foot. It tests the position of the needle with relationship to the foot you have on. You can set the needle or change the foot till you are comfortable that you can control the flow of fabric with those guidelines. Remember that the smaller foot doesn't hold your fabric as steady as a larger foot. I have 1/4" feet for all my machines, but since purchasing the Prep tool. I use the normal sewing foot, make the necessary needle adjustments and have better accuracy.