At the GM Dealership I work at, for body panels and such we use 3M VHB Tabe, doublesided 3/4" 15' rolls. Runs about $35 for a 15' roll at most auto parts stores, you just have to make sure its the "3M VHB". Its the best you can get, I used it to mount my roof rails on, and they are stuck, I can rock the car with them and they don't budge.