To help with carrying my RB67 Pro-S while traveling/etc, I bought a Tamrac N-45 padded suede leather camera strap from BH Photo.
I modded the "original" Mamiya RB67 strap cutting off the attachment clips with all the nylon strap up to the wider "neck-strap" part and sewed them on to the ends of my new Tamrac N-45.
What I now have is an awesome non-slip, padded, suede leather camera strap that I can wear completely over my head/shoulder so the camera rests against my hip. When I'm ready to photo something, I simply rotate the camera around in front of me. Carried this way the WLF is at navel-height for perfect viewing.