Before I got a machine that had adjustable speed, I thought of this idea...bring the foot control up to your hand and see how far to press it for the speed you want...mark that level...duck tape a piece of wood to the back of the foot pedal so that it will only depress to that point. I don't know if this will work for your machine, on my foot pedal the top depressed down over the bottom part. That little edge would have hit the wood at a certain point before it reached the floor. Perhaps you can do something similar? That way when you put your "pedal to the metal" it only goes to the stopper.