Thought I’d post my experience on using Ali Express PTM7950 and Upsiren 1mm 21W Thermal Pads on Vram. Before PTM7950 with stock paste the gpu would be at 2814MHZ GPU and 2514MHZ Memory and Hotspot would max out at about 90-93C running Time Spy Default.
After at 2914MHZ GPU and 2700MHZ Memory with 24C Ambient at 3 Days i get 78.7C Hotspot running default Time Spy. Since then its dropped a little bit more with a screw tightening. I bought the 80x80 as it took a couple tries to get it right but think it would be easier next time. Definately put in fridge for an hour 1st as its like peeling off one of those kids tatoo transfers very thin.
7900XT after PTM7950 and Upsiren 1mm Thermal Pads on Vram bought from AliExpress
Did you overclock your GPU? I used it on my 7900XT (no overclock), and it dramatically lowered my Hotspot temps. It has continued to hold steady after 3 weeks also.