blake, in two Texas songs I can think of right off, Jimmie dale Gilmore's Dallas and Guy Clark's Let It Roll, the word Dallas is just pronounced normally, with a short A. they're texas singers. it's totally your call and makes no difference to me at all. I've just heard hundreds of songs with the word Dallas in it and never heard it pronounced like that. in speech, either. you mention what sounds natural. that's a definite concern...but is it natural to mispronounce a word to force a weak rhyme? better to use a clean rhyme in a way that sounds natural. to me, that's the sign of a skilled, talented lyricist. we've all used shaky rhymes to get our points across. but to pack a song full of them shows a lack of concern for the craft...just shooting for the line of least resistance.

Nashville demos etc:

https://www.soundclick.com/bands3/default.cfm?bandID=431939

other demos:

https://soundcloud.com/wabash-cannibal

Amazon Kindle books by Robert George you may enjoy:

1) Americana

2) Teenage Graceland

3) The Will to Be

4) Fort Mystery

5) Wheel Sea

6) My One True Love