Rolleijoe,
Thanks for your comments.
My problem is that I am trying to do two new things. For years I did landscapes; mostly with 35mm but also on 5 x 4. Now I'm trying to photograph people at work, who have this habit of moving around, and I'm trying to do it with a camera which requires me to look down into a viewing screen. Takes some getting used to.
You mention a Mamiya 7. I was wondering if this could be my solution, as I am very much at home looking through a 35mm type viewfinder. The bigger negative would certainly help to get good quality large prints.
Since you wrote this I see you've gone with using the ETRsi, and marking the screen up for 645.
That sounds like a good solution to me and you still have the full square frame if you want to vary some of your compositions, and it will help if you want any big prints to spice up the exhibition you mentioned (obviously).
But -
I do see what you meant about the shots where people are moving about a lot though. I'm fond of MF rangefinders and have a number of the Fuji ones. The 6x7 and 6x9 machines are wonderful, and comparable to the Mamiya 7 that you mention. But have you thought about the Fuji 645 rangefinders?
The older ones (real rangefinders, not AF) are a relative bargain now, and the GS 645S is a lovely camera for the sort of reportage/documentary project you describe. It has a 60mm f4 lens so is a moderate wide angle with a 'natural' portrait orientation, though it is easy to hold in landscape orientation too. The lens is extremely sharp, and I've found the meter is acurate too. Oh, and it takes 220 film if you want it to, so you can have 30 shots without reloading.
If you find that the ETRsi is proving difficult for some of the more 'action' type shots, the little Fuji might be a very nice addition to, rather that replacement for, that system.
There's not much to go wrong with them, though I had to replace a metering circuit once. The only non-obvious thing really to look out for is is to see if the shutter needs a service.
Just a thought...
Peter