"I actually set at 41 PSI just to be sure I wouldn´t lose all my CO2 cilinder."
This statement doesn't make any sense to me. 3 volumes of CO2 is 3 volumes, regardless of the pressure you are applying. Once you get 3 volumes in solution, the head pressure of 40 vs 50 psi is only wasting CO2 in the headspace (which, in a full 5g corny is very small). The higher pressure is just forcing gas into solution faster due to a greater differential between the liquid and the headspace.
If you are worried that a 9psi difference will blow a post off, I wouldn't worry too much. A corny keg is rated to 130 psi (at least the one I looked at was). 41, 50, you are still way lower than 130.



