However - I can thank John Sherrill Houser for recommending this tool for his class and Victor Issa for for catching some proportional mistakes that weren't obvious but were nonetheless there.
I got my calipers at Sculpture Depot and they reduce to 1/5 or enlarge up to 5 times. I got the metal ones because they would fit into my luggage for the plane trip to Brookgreen, but I like the look of the Polycarbonate ones and will likely get them soon.
I also measured from the ankle bone to the middle of the knee and the width of the ankle bone. Constantly checking in this manner is a wonderful way to keep things in check and to identify an area that may be out of proportion. I'm in love with this tool and it's my new BFF of my studio and use it for many measurements throughout the entire figure.
That said - the caliper is a mechanical device and won't dictate exactly what I do. There are times when deviating from the model's measurements is an artistic and deliberate choice made to enhance the figure, make the pose more dynamic and interesting or to make an artistic statement....as long as these choices are made by the artist and are not a product of accident or laziness.