Mamiya RZ67 - Does anyone use the 6x6 or 645 film backs?

[MatthewOsbornePhotography]

Hi guys,

I have a Mamiya RZ67 Pro ii medum format film camera with 2 standard 120 6x7 film backs. I love the camera despite it's size, in particular the huge bright viewfinder. As film is now getting quite expensive getting 8 shots on a 120 roll is not that cheap.

I have 2 different 'wants' from the Mamiya RZ...

1) I much prefer 6x6 to 6x7 format. I have 6x6 film bodies such as Pentacon 6 TL, ARAX-CM & Kiev 88 but I much prefer the viewfinder of the RZ to the other cameras. I realise I can crop 6x7 photos but I prefer the original square negatives uncropped. I thought if I got a 6x6 film back I would not need my other 6x6 cameras.

2) I want to use the RZ more for wedding photography to replace my Contax 645 as I find the RZ more rewarding to use. Shooting 6x7 for wedding portraits is not that economical so I thought it would be perfect if I got a 645 back for the RZ (so I get 16 shots per roll instead of . It means I can then sell my Contax 645 which I find too much like a DSLR. (It's too easy!)

So, my questions are -

i) Has anyone used 6x6 or 645 film backs on a RZ67?
ii) Do I have to mask the VF and if so how do I know what part of the finder is the square or the smaller 645 rectangle?

..I realise I will not get the full benefit of the 6x7 format using cropped film backs but I am trying to make the camera cover multiple needs. I think even smaller 645 negatives are still 100% better than 35mm negatives. I have 35mm Nikon FM and Voigtlander Bessa R3A bodies but I don't think the photos produced would be that different from my 35mm digital photos (Leica M9 + Nikon D800).