Whelp - good news and bad. I didn't wreck the card, and the repaste dropped gpu and HBM temps down by about 15 degrees - while hotspot dropped about 10.
Bad news is the 5w/mk generic blue pads from Amazon performed near *identically* to the yellow pad asus used for the VRMs. I topped out at 108 degrees after about 30 minutes of Furmark. I guess the Minus 8 pads and/or the copper shims are the way to go.