I have not tried the thermal right pads, but I ran into issues with the Gelid Ultimates:
3080 FE Thermal pad mod: Don't use Gelid Ultimate 2mm pads. | Overclockers UK Forums
roger, I'll report back how it goes when they show up from China. I've not used them before either, so I figured an extra 0.5mm sheet (as well as a 1.5mm) should cover the bases. I'll probably only do the back to start.