You asked a specific question and Regards provided you with a good answer.
Concerning your rule, it is correct.
But, taking into consideration your example sentences, the preferred plural of "person" is "people." Persons is acceptable, however, and you second sentence is correct. Yet, I think most people would use "people" and not "persons" these days.
I'm not a native but I, too, feel my second sentence is correct. I discussed it on another Forum and a native speaker replied to me that both forms are correct. Now you confirm my feeling. So thanks a lot (to you and Regards). (My example sentences aren't actually mine; I found them on that Forum.)