I have just used some Arctic Silver ASTA-7G to fit all the sinks to my reference 7970. Good job I did a decent job as I doubt they will ever come off again.. 
I have not tried it yet as I'm loving my 680 to much at the moment but will try later.
I love the quote on the fitting instructions.

I have not tried it yet as I'm loving my 680 to much at the moment but will try later.

I love the quote on the fitting instructions.
Precaution:
Arctic Silver Thermal Adhesive is a permanent adhesive. Components you attach with Arctic Silver Thermal Adhesive will
stay attached forever.