This is another example of the great work on Dr. Kevin Kirby. After I measure that angle, and you can get a feel of when your orthotic prescriptions should be changed. Work has to be done to note how this correlates to the heel eversion measurement I use to predict my Inverted correction. Say, when above 16 degree deviation do you add degrees of correction from a Kirby Skive or an Inverted Device. I have my thoughts. Thank you again Kevin, Rich Blake