Hi guys, My Stillen GTZ type 1 urethane bumper has cracks on the two nubs on the lower edge of the bumper cover and the paint is discolored and has cracks, so I'd like to fix it. I've done some research on how to do this (reinforcement patch on back of crack, grind a V on the crack to fill in). Will this work to fill in/repair the crack after the above? It says it is for flexible plastics, so does this include urethane, too? Also, should I grind the V on both sides of the crack, or just the front? Thanks!