Gary Goodman has a custom 12 string bass in straight 4ths using his custom made strings. He covers the same range as an Imprerial Bösendorfer (8 octaves). I think this is as far as you can go with physics and I believe you hit practical limits before; can you imaging playing a string that is .250''?

Daniel.

If I recall correctly, Goodman also sells a customer set of strings that he states will withstand the tension of that extreme tuning/string arrangement.


Take care,

Paul

I play NS/Stick with the lowest E and high string Eb. In my opinion, that tuning is the most convenient for 8-strings instrument. And for 4-strings bassists)).
For example - http://www.youtube.com/watch?v=j8OeVet7ecM
And my second tuning with the lowest E and high string Eb, but melodic strings are octave down. The same C,F,Bb,Eb but octave down.
For example - http://www.youtube.com/watch?v=wws_xz9_eUQ
For bass side I used four bass strings, and for melodic group - four guitar strings. In the first tuning - four highest guitar strings (.010, .013, .017, .026), in the second tuning - four lowest guitar strings (.017, .026, .036, .046)