Ernest made the comment about gun straps but he is about 35 years too late. One of the absolute best banjo straps I ever had was taken directly from a tankers .45 caliber shoulder holster. And those current straps which use a single buckle with the tang built in (a short metal strut sticking straight up in the middle of the buckle) follow that M-42 shoulder holster model. I did this to my 63 Vega upon my return from the 'Nam, and the strap worked great for about 25 years. I now have a similar arrangement using an old Fender 50s style, narrow guitar strap.

And yes, thespionage, the only way to strap on a long-neck is over your right shoulder with a short strap attached to a strap button on the underside of the neck heel, so that the strap rises from that point under the neck, goes across the front of your body, then over the shoulder and ends at the banjo pot near the tail piece. The strap should be relatively short, and just allow your right hand to slide in, and the pad to make your shoulder. It allows you to balance the longer neck in your left hand and puts your right hand on the head at the right spot. If you need more upright angle on the neck, simply push down on the pot with your elbow as you play. A little practice and it comes naturally.