For what it's worth; 1850's "Minstrel" banjos were pretty big - up to 14" diameter pots, gut strung - and usually tuned a couple of steps lower than modern "bluegrass" instruments. although not a "bass" by any stretch, they have a very different, unique sound.

A local 'Catter has a "Ban-jar", or 6-string guitar-banjo, with about a 15" head and one helluvva sound. Since I played banjo before taking up the guitar, much of my fingerpicking style has evolved from banjo techniques, and it was certainly interesting to play this hybred. Although not at all common, they do show up from time to time, and this is not the first one I've seen. There was a guy noodling around on one at a Civil-War reenactment once, which was totally inapropriate - but there are other genres to which I would gladly bring one. If my Amigo ever considers parting with the beast I would be tempted to dicker.