I was able to repair my front bumper with a soldering iron and zipties (plastic style of welding), it was very rudimentary, but actually worked filling small wholes. I might try sanding it down see if that makes it look better. I have a second front bumper has a 1 1/2"X3" hole, on the bottom. I was wondering if anybody has tried using fiberglass to repair them?
Body shops have ABS plastic welders, make a friend ad give him a few beers to do it after hours, works great