I was more or less thinking along those lines. Still, I'm reluctant to call something like that on my own. In my work with butterflies, I've encountered folks calling something a rarity, or slightly outside of its reported range while overlooking something much more common that turns out to be the correct ID. I'd rather not do that.

This one was photographed in the Atascosas, which is a bit west of the ranges you suggested it might turn up in. I found it on two sites about a half mile apart. There was ample similar habitat in the area. Although you can hear them when they fly up, they don't make a buzzing or crackling sound- certainly nothing like, say, a Circotettix. I took a couple of specimens, which I'm mounting. I'll post a photo with the wings spread when they're dry. Thanks again for the ID.