[rotorwrench]

There is nothing wrong with a bit of filler. They make spray polyester now days so you spray it on like primer. If the metal is straight enough, that's all that is needed. It's just like the old lacquer primer filler in a way. When the filler gets thicker than 1/16" or so the it becomes something that may be a problem if the car sets out in the sun for long periods of time. If the filler is in the mil thickness range then it's not much different than paint.