In analyzing the data, I found that 7-20-7-20-7 on a single frequency worked better than just 1 hour straight. The people who used the 7-20 method reported better results.
People who used 5-20-5-20-5 did not get good results and this supports Dr. Clark's minimum of 7 minutes per frequency.
We also found that using 2 frequencies in the equivalent format produced even better results. 7-7-20-7-7-20-7-7 where 7 minutes was spent on frequency 1 and 7 minutes in frequency 2.
Oddly, at 15 Hz, 1 hour continuous may be better but we did not collect data on that.