I have the Mamiya 6 RF and Fuji G690BL . If you are finding the Mamiya 7 RF too large the 690BL is even larger and heavier… by a lot.
Great camera but it is big, slow and highly noticeable. Not what I like for discrete street photography. But you could do it, I guess if you set your mind to it anything is possible.
FWIW if you are spending that kind of $$ I’d suggest a Canonet GIII QL17 , fast , sharp glass and a medium range 40mm lens
Here’s Gandy’s write up if you haven’t thought about this camera before.
http://www.cameraquest.com/canql17.htm
Here’s a shot taken with the Fuji G690 BL w 100mm lens, it was posed by a bunch of kids who wanted their picture taken while I was shooting architecture.
http://www.rangefinderforum.com/photopost/showphoto.php?photo=38020&cat=5267
http://flickr.com/photos/jann/226810915/