I also like the theory on the guitar. I can't find the diamond pattern on old Dobro's, possibly because it's a "knock off". I'll admit I wondered that at one point in time when I read Dobro lost their patent but didn't follow it up, guess I should have. My grandpa always told me to make sure I loosened the strings after playing to prevent it from warping so I assume it's early and without the support rod.
Even with the truss rod, the neck can warp. Some argue for loosening strings, and some argue against it. Either way, it's the climate changes that do a number on them, and not so much the strings.
