Don't really understand the point in 8 string guitars really. Just take a 7 string and tune it down. Assuming you want to tune ridiculously low (let's say F standard, which is) your high E string is still going to be an Bb, which isn't really that low. And I'm yet to see or hear ANYONE play super-low tuned djent music do anything constructive with the high strings at all, never mind the high strings beyond the 18th fret.