Intersting thread - I agree that if you want to produce a banjo sound then you have to learn to play banjo. However, I have been restoring & making banjos for a while now & although this diverts from the original question i have just come across a banjo with seven strings one of which is an octave string. It needs a bit of work to make it playable but if anyone has info as to how it should be tuned please let me know.
Its not one of those Windsor types which had a spare tuning peg, this has seven tuning pegs and a seven pin tail piece.