Welcome back JD.
IMO (personally) you were right: testing blocks with air/water temps outside of a normal range is a whole different kind of testing, and if compared with a normal block test, can seriously skew the results. Let's see the "Cascade" tested with sub zero coolant temps, and get this out of the way, once and for all
(Oh, if I had my tools with me!!!)
So is this direct die cooling block using the same top you've had for your last trials?