Greetings, Mamiya users;
I carry two bodies and three lenses, plus some b & w filters and other sundries, in a Billingham "5" series bag, black. The bag has a comfortable padded shoulder strap and it can hold enough gear without feeling too heavy (for me). I have the 50, 65, and 80 lenses. I keep the 80 and 65 mounted on camera bodies and the 50 in a pocket. I have the standard issue Mamiya shoulder straps on the cameras and carry one camera on a shoulder and keep the other in the bag unless I'm in a situation where I need to use both the wides and normal focal lengths, or when I'll need the full 20 shots both bodies can deliver, then both cams are out of the bag. I don't like to change lenses on this rig in the field, as it takes a couple of minutes, and one has to be a little careful. Both the 65 and the 80 are fine, but if it came down to just one lens and one body, I think I'd go with the 65. I'm thinking of getting the 150, equivalent to about 70mm or so in 35mm format, but I'm guessing I wouldn't use it all that much, not enough to warrant carrying around its 1 pound bulk in an already full bag. Love the camera, though. Perfect as a travel kit.
Regards, Chas