Sounds interesting Ian.
As I haven't got a head in front of me, do you actually have to remove the core plugs and drill/tap to suit whatever the thread size is of the fixing you're going to use, or are there actually tapped plugs in the head already (to seal up some of the post-casting machining channels) that you simply remove and replace ?
Thanks for sharing the info Ian.
PS If you're not using that 909 fitting, is it for sale ?