Jose A Martinez,
We haven't mentioned "reciprocity law failure" which means you may need to give even longer times if you are running into exposures longer than 10 seconds since you are using a pinhole...
An old chart says it:
If indicated time is ... give this much time
1 sec ... 2 sec
10 sec ... 50 sec
100 sec ... 1200 sec
Curiously, it is about the same as placing exposure on Zone VIII ... I wonder ...
Is the whole purpose of moving exposure to Zone VIII supposed to correct for reciprocity law failure?