mold in question. this is for the bottom of glove box that needed to clear a larger than factory delux heater. A lot of the masking tape pulled off when I made the bottom, but I was able to re-use the same mold without that notch at the back to make the top half and used packing tape for the top.
For the bumper I would not rely on tape. I could destroy the cardboard mold if needed and deformed it quite a bit getting bottom out. Bumper would not be so forgiving
I'm contemplating a headliner molded on roof. Someone on here did that but never posted the final results