Well my 645-67 pentad adaptor showed up today in the mail from Singapore, used purchased off of bay.
So I went ahead a put on my Pentax 45mm 6x7 lens and went out shooting,
Oh boy, no good.. sharp 2/3rds of the frame and the other 1/3rd"corners are no good, soft with cyan CA, which is correctable, but again 45mm not happening on the 645D.
Now I have tried a 645 45mm FA, 645 45-85mm FA zoom, and now the 67 version of the 45mm prime, best result by far so far is the zoom.
Hard to tell in these jpgs I created in Lr3 1600 pix wide SRGB, but if you looked at the original DNG files at 100%, night and day difference.
Here is the 45mm 67 at F13 LR3, cyan ca -20
Here is the 45-85mm FA at 45mm F13 AF LR3
Steven