[DanEC]

I don't think aluminum sheetmetal has any memory like high strength steel so working one out may be a bit different for most of the PDR guys. If you can get to the back side with a blunted end rod like a punch and tap it with a hammer - you can start at the outside of the ding and start pecking it out, working in a spiral pattern towards the center. This is how dings are removed in stainless steel trim during restoration. Keep checking with a straightedge as you go to make sure it's not be stretched too much outward - but it has to go out to flush or very slightly higher. At this point there will be a bunch of small dimples slightly above profile and they have to be filed down flat and then the filed surface worked with increasingly finer grades of sandpaper on a hard surface sanding block, until it's down to the finish of the rest of the body.

A lot easier to describe than to do but this is how I've restored a number of stainless trim items and they come out flawless. However, I suspect getting enough access behind the dent to tap it out may be a problem.