I've added a vertical neck strap to my website gordy's camera straps.

Not many cameras come with the right lugs to do this. The Leica M5 and Leica CL did as well as the Voigtlander Bessa R series with the trigger winder. This strap lets any camer be hung vertically if it has lug mounts and a tripod mount. Personally, I like the vertical mount. Particularly if you have a heavy lens. It's won't flop over on you.