If you don’t want to open up the computer at all. Another way is in windows, go to “edit power plan” > advanced > maxmium > 99%. This disables turbo mode which heats it up to 100c.
I used aluminium foil instead of a copper shim. The benefit is that you can adjust the thickness by folding it up however much you want.
I put the layers like…
* CPU
* Thermal paste
* Original copper heatsink
* Original thermal pad(on top of the copper heatsink instead of under it)
* Aluminium foil folded up, 4 x 30cm foil.
Mine went from 90-100c down to 55-65c under full load. Using the 7zip benchmark test to get to full load.
The screws on the case are shorter on one side. Make sure you put it all back with the right screws so that it squeezes the copper heatsink onto the cpu.