Good idea. I'll look into adding a via to help heat get to the thermistor. I was thinking about having sensors for each quad but didn't have enough inputs for individual monitoring. The idea of averaging via several is great because the thermistors are cheap. If I put two in series in parallel then I get 4 thermistors with the same total resistance. I do see some issues with this for situations where not all ASICs are installed or when one gets to critical temp when others are fine. In the latter case you're no worse off than just having one, for the 3 not monitored, but in the case with less ASICs the average of the installed ones would be impacted.