If we own or play 6 and 7-string banjos one of the most noticeable differences is their closer string spacing when compared to the 5-string. However, there is by no means a 'standard'; even among the small sample of these instruments that I play there is significant variation. I'm interested in collating information here from owners of 19th century 6 and 7-string instruments (regardless whether subsequently converted to 5-string use) on neck widths to build a picture of the range used by the original builders.
Width at nut (and slot spacing).
Width at drone string peg.
Width at rim.
Original bridges for 6 and 7-string banjos are often long gone. I own one likely original 7-string bridge; if there are others out there the dimension/slot spacing of these would also add to this picture.