I was going through the message boards and found your message again and was wondering if you were able to find any further information on your dad and his family. I feel confident that, at the least, your dad was probably a cousin to my grandfather since grew up in kind of the same area. My great grandfather was John Patrick O'Flynn (aka J.P. or Johnnie) and married Vila Finch. J.P. was one of 11 children and he and Vila had 11 children. I do know that there are some O'Flynn's in the Hattiesburg area who are cousins and are related to J.P. in some manner. Our O'Flynn/Finch reunion is coming up the end of next month and your are more than welcome to attend. It will be in the Laurel area. You can contact me via my email address for more details: firstname.lastname@example.org
I'm sure that some of my great uncles MIGHT be able to offer you some insight into the O'Flynns who live in the Hattiesburg area.
I pray this is some help to you.