Tiger Hair is good stuff. Basically the same as kitty hair just slightly longer strands of glass. It's a little stronger but as with any body filler is should not be over used. I had voids on my kit that I first filled with milled fiberglass and resin( more structural). The way I look at every square inch of the car body is if that area were to flex or take an impact like a rock chip will the area hold up to normal road conditions. Just make sure after all the time,money, and paint is on it- your worst fear would be for something you caked filler on to fall off.