Bondo Glass Filler does contain short strand glass fibers. However, it is only recommended for holes approximately the size of a dime or smaller. Bondo Glass Filler will perform better over a 2" void than the regular body filler (without glass fibers), but it is definitely not best practice. For example, a body shop would cut out the bad metal and weld in a patch, using filler for final shaping.
Saying that, it would be a better do it yourself repair if the hole was first reinforced from the back with the Bondo Fiberglass Repair Kit (fiberglass mat and polyester resin), then filling the repair with the Bondo Glass Filler on the front.
answered 2 years, 6 months ago