The problem with using a sax type strap on a banjo is they are a very heavy instrument as opposed to a clasical guitar or sax hanging on your neck and would probably give you neck problems in the end. I once played a ceileidh for about 4 hours standing with a banjo and melodeon, next day my right shoulder ached from the melodeon and my left with the banjo and I could hardly move that evening. Since then I have always sat while playing for a ceilidh.
Bill