So I got the WD15EADS, used wdidle, and that worked great:
Code:
9 Power_On_Hours 0x0032 100 100 000 Old_age Always - 60
193 Load_Cycle_Count 0x0032 200 200 000 Old_age Always - 4
As a sidenote, wdidle just runs on *all* disks, I had an old WD 20GB disk connected at the time and it tried to disable the idle timeout on that disk too. meh :-/
I also had the chance to get my hands on some other WD GP disks such as the WD10EADS and WD20EARS, and wdidle worked on those too.
... When I look on the interwebz I get conflicting reports about which drives do and don't work ... Internet sucks.