I don't have the larger HK passive heatsink myself to be able to test but I think it might be possible to avoid nearly all throttling on it if you can get the voltages down a bit. This is how I think I'll look to run my N1 long term as I don't think the fan will be needed much at all with a little tweaking

I ran a bit of a test/benchmark below as a proof of concept and to gauge the performance gains available. It takes a while to work out and test the lowest stable voltages but at least it translates to something this time

Run 1:
Stock CPU voltages
Stock active cooler - fan disabled (running passive)
test: Compiling N1 kernel

First throttling occurs after 171 seconds
Average clockspeed: 1586MHz
Average Temp: 80.2C
Run 2:
Undervolted to lowest stable voltages for my sample (-87.5mV to -112.5mV on A53 cluster / -75mV on A72 cluster)
Stock active cooler - fan disabled (running passive)
test: Compiling N1 kernel

First throttling occurs after 302 seconds
Average Clockspeed: 1796MHz
Average Temp: 78.4C