All, Below is a link to an article called "How to Calibrate Your ASI." I believe it was written about 1989 and published in Kitplane magazine. While I have not tried this yet, but after reading it and thinking about it, I believe it shows promise to being a realistic, accurate, and inexpensive method to accomplish just that on an Ercoupe.
http://www.rst-engr.com/rst/articles/KP89JUL.pdf John Roach N 2427H
