i do use thermal pads (these are quite good) https://www.aliexpress.com/item/ARSYLID-High-quality-100-200-1-0-2-0-4-5mm-Thermal-conductivity-3-6W-CPU/32835108024.html?spm=a2g0s.9042311.0.0.4fd54c4d3E82Yb
0.5 mm or 1 mm and a copper shim, 1 mm thick or more https://www.aliexpress.com/item/20-pcs-15mmx15mm-0-3mm-0-4mm-0-5mm-0-6mm-0-8mm-1mm-Heatsink-Copper/32826278552.html?spm=a2g0s.9042311.0.0.3dbd4c4dpaqYyI
I experiment with the thicknesses so that the stock heatsink presses the shim and the pad slightly without being thicker than the processor height (been there done that, and the GPU fan was squealing ) the more spacious the copper shims the better, however, i do this on rough estimates, that the memory die consumes 1-2 watts each (reasonable?) the shims not touching the aluminum directly is not a big problem, because copper blown by the gpu fan imho is more than sufficient to cool the memory. Most of the Aorus 580s i have memory cooled from the factory reach 2100-2200mhz (8 gb, 4gb all of them hynix) i found thermal pads being 0.5 mm and perfectly matched with the heatsink, but, as a consequence of mining these pads will dry within months (become brittle)

Do you really clock those elpidas to these clocks? lol? how do you cool them? what sort of timings for such clocks!?