I don't know how large or small the population of TB users is that play metal or extreme metal, but I found a book you may find very useful.
Amazon.com: Extreme Metal Bass (Book/CD) (9781423497158): Alex Webster, Cannibal Corpse: Books
It's written by Alex Webster, and is loaded with info on the genre, in terms of bass line writing, technique for both right and left hands, rhythm, and exercises.
I'm really only scratching the surface, because there's a ton of well worded and well explained things in this book that have made me noticeably improve over just a couple days.
Just throwing this out there, I know there's not a lot of info to be had on the genre, and this helped me immensely.
Cheers!
Amazon.com: Extreme Metal Bass (Book/CD) (9781423497158): Alex Webster, Cannibal Corpse: Books
It's written by Alex Webster, and is loaded with info on the genre, in terms of bass line writing, technique for both right and left hands, rhythm, and exercises.
I'm really only scratching the surface, because there's a ton of well worded and well explained things in this book that have made me noticeably improve over just a couple days.
Just throwing this out there, I know there's not a lot of info to be had on the genre, and this helped me immensely.
Cheers!

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