Eduardo, Bill,
I struggled with replicating the p indicator for a while (nice name by the way, it denotes probability p). It is true that for some reason Michael Harris is secretive about it after his second book. I concluded though that you can simulate the performance of the indicator if you follow these steps:
(1) Use APS to find patterns for a specific instrument. You need a good number of them.
(2) Monitor the signals generated by the patterns
(3) If you get more than one signal then P = sum(hist. trades x hist. win rate)/sum(hist. trades) over Ns, the number of signals.
(4) If you get both long and short signals, then the win rate of the short ones is a negative number
(5) You then look at the P value AND the number of signals (Ns). For example, you may decide based on historical testing that it is best to trade when P > Pmin AND Ns > 3.
This has worked for me and it still works well but you must do your homework and set your parameters to the right values.