It has been my experience, with most software, that you can simulate and measure draawings all you want, and when you cut the work, it will not be the same as the drawing. Cutters flex, and they wear, and the work vibrates. My advice to you is to learn to leave stock for finishing and then take a finish cut that cuts just a small amount. Typically, you can rough cut something and leave 0.010-0.020" and this will allow you to increase the speed and feed and take deeper and heavier cuts. Even with cutter flex and wear, you should still have enough stock to finish the cut and get a good finish.