I did it. Huge thanks to u/ElectronicHair2283 for the tip about mini heatsinks, the SPD HUB temperature dropped from around 50 C peak to ~47 C.
Approximate size for Hynix A-die is 9x9x5 mm, you can go a bit larger, maybe 11×11, but I couldn’t find any that stay under 6 mm in height.
Previous post about RAM heatsinks:
https://www.reddit.com/r/overclocking/s/056GlBn8wy