filler, of any type, is a skim coat over good metal to make it look straight. It is not a replacement for gone metal, it will fall out. It is used as a replacement for craftsman level metalworking that doesn't need filler when done. I can't do that level of metal work, nor can I afford it.
There have been may lazy ass ways to try to get filler to stay, chicken wire, stuff it with newspaper, whatever. all fail and all fails.
They say there are no such thing as a stupid question. They say there is always the exception that proves the rule. Don't be the exception.
