[tuner]

How big a patch, let's say in square inches, do you think the limit is for putting bondo on a rusted-out spot on a car? I plan to grind the rust away, and use some cloth on the inside of the fender I'm working on, but I really don't want the patch to fall away after all my hard work - and especially not after a paint job!

[philio]

You might consider taking it one step further if you have the tools. You can get a metal material that is a very fine mesh and weld the hole. Then you can use the bondo over that. Just a thought.

[spinner]

I think philio's idea sounds good - a friend of mine did the cloth thing and had a hard time getting it shaped to the car's concavity. A metal mesh might hold better.