I have and I can confirm (QX9650, C0).
The system is pretty much like yours, H2O with a *huge* Reserator 2 radiator.
Left the system unpowered overnight and the whole thing including 1 litre of coolant (+ 7kg radiator) was 20 C at the morning. Booted to idle: core 2 and 3 read 10 C in RealTemp. That is 10 grades below ambient.
Now I'll PM my log to uncle :-)
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