I have friends who are avid collectors of old Missouri tunes. They often modify the measures of songs so they can be used for square dancing etc.

My own choice it to listen to a song and do it the way I think it sounds best. Usually it is the odd phrasing or strange tunings that attracted me to the song in the first place. I believe this is how it was been done historically. That is also why regional styles developed. Since local musicians shared music and techniques they tended to evolve a similar style.

Unless you are trying to learn or demonstrate a particular person or style there is no reason not to do it the way it sound best to you. Chances are that is how the musicians you are trying to copy did it.

RPr