While wrapping up my DIY build I discovered that the module will always hang on writing factory wavetables to extflash. I suspect it might have to do with some of the flash mapping changes since ~2.0, but I am not sure.
The current path to get a DIY module working is to flash ~2.0 with wavetables included then upgrade after the fact as far as I can tell.
If I have time I'll run a git bisect to see if I can track down exactly what's wrong and fix it, but, uh, I'm a ruby programmer so this is mighty out of my wheelhouse.