I have never been able to master the start/stop feature on my machine because I use two hands to manage the fabric and that leaves nothing to push the button with. I always feel like I do when I drive on icy roads with cruise control. Everything could be fine but if something happens I don't have control to react. I use the speed control on my newer machine and on my older machine that doesn't have speed control I just know where to press the foot pedal. It's a lot like driving the car with the accelerator.