A couple of minor points. Locally a Harvey Reid an acknowledged musician uses a six string "Guitar Banjo" as one of his many instruments and does quite well on it.

Although the fifth string on a five string banjo isn't fretted - it's a bit far down the neck to fret,with the rest of the hand up at the top of the neck - it creates a problem when capoing the banjo, so several work-arounds have been done. The one is one or more small brads driven into the fingerboard below the level of the fifth string. The fifth string is hooked under one of these brads to act as a fifth string capo. The other, more usable method in my estimation, is a small rail connected to the rear of the neck, just behind the fifth string peg, with a small movable capo that slides up and down on this rail, and adjusts only the fifth string. It is small enough that it won't interfere with the regular capo when the capo is adjusted lower then the fifth fret.

Dave