Even though thunderbird necks tend to break...I think that mahogany necks with that straight grain may be less prone to warping or twisting and tend to stay true. This has been my experience. I have had two maple necks go wonky over the years. The cool thing about the zebrabird edition is that the mahogany neck/centerboard is unfinished...an has it's natural almost orange/red color and . I think the natural epi pro may be unfinished as well, not sure...
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And the fact that Thunderbird necks are laminated with about 5 main sections of wood. That's huge in preventing warping and is likely more of a factor than the Mahogany, though that certainly is part of it.