Phil,
iView have just released 3.1.1 of MediaPro which now writes to the data fork for CR2, NEF and DCR formats. So, RSRC reading and writing would olny be needed for CRW.

I did notice in the version history that ExifTool build 6.21 "Changed CR2 identification logic to properly identify CR2 images which have been edited by PhotoMechanic". Is this something you would look at also to handle iView 3.1.1 annotated CR2s?

I'd be interested in any info you can provide around the 'safety' of using both iView and ExifTool interchangably to edit CR2 images.

Thanks,
Mark