Yah, that is basically the idea.
You would use like a 5-3mph reading as the basis for computing rolling resistance, then use the 55-50 to compute CDA (which the program would subtract out rolling resistance). Yes more runs, in both directions would help, especially if it is easy to use. And if you enter the displayed CDA and RR numbers into a web page with your zip code shortly after the tests, it can look up your current temperature and pressure for you and print out "corrected" CDA and RR figures
