I reached out to the good people at b-grip, an Italian based company that recently released the UNO, a carry system designed to work with mirrorless camera systems. I've had this for about a week and I wanted to give you some initial insights as I am adjusting to using it before my travels to Peru in mid May.
Construction & Design -
The UNO is a "high resistance techno-polymer" that contains glass micro-spheres as well as fiberglass. Although it appears to be high grade plastic at first glance, this mount is definitely tougher than expected (no flex/warp/discoloration under stress). One of the big differentiations with this mount is that on the chest mount it allows the camera to hang pointing directly down, not resting on the mount or strap. This seems to prevent the camera/lens rubbing on the mount (note - the b-grip UNO needs to be mounted at mid chest or a touch higher, otherwise if mounted too low it is not as efficient for accessibility).
The UNO mounts in two manners - a compression bar for the shoulder strap mounting option or a belt/pocket hanger option. I have zero interest in the belt option, so my tests will be solely on the shoulder mount. On my initial walk around, I may use some paracord to attach the bottom of the UNO to the shoulder strap to prevent the system from 'flapping' while climbing around.
Arca Swiss Plate
The UNO has an Arca Swiss style mounting plate made out of the same techno polymer as the rest of the system. This plate is very basic, with a rubberized surface between the plate and the camera. This works great for my Sony A7r but I noticed that when mounting it to the Sony A6000 it was tight against the LCD and I couldn't easily tilt out the LCD. I will likely be shooting with the A6000 more on this system than the A7r, so I am curious to see how much 'annoyance' this causes.
I have also mounted my GoPro Hero3 on this system and I really like how it fits well with the UNO. I have a feeling I will be doing more GoPro video and timelapse now that I have something besides my crazy head mount!
Ease of Use
The locking system is nice, I felt very comfortable in my initial walk around that both cameras were secure and I wasn't going to lose them. In my attempts to 'quick draw' my cameras I found the system to take some time to get acquainted so that I can quickly get the camera out and ready for shooting. I need a bit more practice with this before I can feel confident in using this over something like a Rapid Strap.