Hi Ron,
I know from experience that the method works great in stock indices but you get a larger sample size in currencies because you have more two way trade. You also have interrelated markets -- correlations -- in currencies which we use as a filter. The S&P 500 and the DJIA were one of the first markets I saw the Dow tenet phenomenon that is the core of this method in.
For me stock indices are an investing market and currencies are a trading market.