Rangefinder Test, 2012
Mamiya 7, 150mm Mamiya N
TMY, Pyrocat HDC
I just gave your recommendation a try, and I have to admit that it worked much better than I had anticipated. This photo was made to test the accuracy of the rangefinder at medium distance. I got the high reading from the window itself, but I exposed for the shadow reading, as recommended in the BTZS book.
To me, this illustrates one of the advantages of incident metering: not having to pre-visualize. Almost everything in the subject is white, and there was nowhere obvious for me to place any of the zones. With this approach, the zones (many of which don't fall on a roman numeral if you know what I mean) took care of themselves.