I think we have the answer ladies and gentleman - stock mount fails, Noctua mounting kit FTW
Wraith Stealth
3.7 @ 1.2v: 31 degrees idle and 74 degrees stressed
3.8 @ 1.35v: throttles at 100 degrees
IS-47K with Stock Mount
3.7 @ 1.2v: 40 degrees idle and 79 degrees stressed
3.9 @ 1.35v: 40 degrees idle and 90 degrees stressed
IS-47K with Noctua Backplate
3.7 @ 1.2v: 30 degrees idle and 65 degrees stressed
3.9 @ 1.35v: 30 degrees idle and 82 degrees stressed
EDIT: @Thehack can you get in touch with ID-Cooling to verify this also pls?
Wraith Stealth
3.7 @ 1.2v: 31 degrees idle and 74 degrees stressed
3.8 @ 1.35v: throttles at 100 degrees
IS-47K with Stock Mount
3.7 @ 1.2v: 40 degrees idle and 79 degrees stressed
3.9 @ 1.35v: 40 degrees idle and 90 degrees stressed
IS-47K with Noctua Backplate
3.7 @ 1.2v: 30 degrees idle and 65 degrees stressed
3.9 @ 1.35v: 30 degrees idle and 82 degrees stressed
EDIT: @Thehack can you get in touch with ID-Cooling to verify this also pls?