one of the advantages of a WLF is the much brighter image....of course tracking movement left/right is tricky......but for portrait i find it still the best....
i thought the Hy6 would accept the 6008 finders? there are several available and prices are not that bad (on ebay)....
of course because the back can be....."rotated" on the Hy6, the prism finder will have quite a bit of black surrounding the image, which might be distracting....none of the 645s (hass, mamiya, contax) have to deal with that.....i know this from shooting with the RZ and the prism....although the actual image is bigger? then on my 645afdII, it feels smaller because there is so much black around it...(of course the RZ is "worse" then the Hy6, it is 6x7 instead of 6x6, so even more black) using the flip-up finder works well, but at that point i feel like i am a foot away from the camera......nothing is perfect....