5 strings is standard, 4 will cost you extra ( ! ). 6 is also an option, and possibly more too as they're completely handmade to order.

Here's a comment about fret lines and please, anybody else who has had this experience or noticed it please reply. I'd like some feedback.

I had a fretless Carvin 6 string a few years ago and Carvin, for some reason, used synthetic lines rather than maple or some other light wood. The fingerboard was ebony. The problem was that the lines were not perfectly flush with the rest of the board. So, while lines are supposed to help with intonation, in this case they caused problems. I believe that when the bass was built the lines were probably fine, but because an ebony board will shift and change with temp and humidity, plastic lines will not. I figured I would have to change the lines out so got rid of it.

My BNF5 here has maple lines but because maple is much less dense than ebony the lines have expanded very subtly in a few spots on the neck. Not a big deal, I'm going to have the board done. My Roscoe LG3000 has an epoxy Jaco treatment on the board, this seals the board so there are no issues with temp and humidity affecting the lines, it's perfectly smooth. I'm contemplating doing this to the F Bass. Like a Pedulla Buzz Bass.