I bought one of the dual format 6x17's recently it one of the earlier versions and haven't looked back the poor rb67 is redundant (atm)
Mine has strap lugs but i would not like to carry it around my neck ala 35mm its quite heavy and if it bounced up and the corner hit you in the chest it would leave a bruise.
its not the most ergonomic camera but very simple ive got the knack of loading film and can reload quickly (but its a bit fiddly you need to line the slot in the spool with the tounge of the winder - press down and tilt the spool into the camera) the receiving end is simply a spigot on a spring push the spool down on the bottom spigot and tilt in - thread the film onto the spool wind on until No 2 is in the window frame nos are 2 5 8 & 11 for 6x17
The film mask is in effect a pair of baffles which change angle when the smaller sizes are selected there is a slight light bleed past the baffles nothing to worry me. I an not sure if the newer models are the same.
Speed of operation would be comparable to a fuji617 as the lenses are basically the same - ie most lf lens can be made to fit with suitable cones i have a 90mm 5.6 SA on mine. Mine has a dark slide the fujis dont (so im told) so you can change lenses mid roll if you want to.
Helical focus ? yes mine has it i dont use it i prefer hyperfocal focus but that said my camera has a removable focus screen which you can check your focus and composition if you wish - calibration for infinity is important to set focal distances on focus ring i spent about an hour setting mine correctly and verified with a tape measure indicated distances were accurate - using focus screen for each and every shot is not possible you would need to be good at estimating distances and focus and set f stop accordingly
Hand Held??? yes but ..... its heavy its much easier to set up on a tripod so that you keep the image square and level (ie horizon parallel to top of frame)
The only problem ive had so far is light getting in through the dark slide slot but i had the end of the camera pointing straight at the sun when i pulled the D/S out i lost 2 frames. It only did it once and the camera goes every were i go i now leave the D/S out (i dont change lens so not necessary) and no more problems.
Compare to fotoman or art panorama - as i understand it fotoman are no more but stock is still out there - ive looked at one fotoman close up they are very similar in construction and cost (gaoersi a bit cheaper) as for art panorama never handled one and the real ones ive seen sell on ebuy have been much much more $$ than either Gaoersi or fotoman
i like mine it does what i want it to do