Engraving Aluminum

Hi all,

I need to engrave some control panels and will
be using about .090" aluminum sheet. I was
wondering if anyone knew what type and temper
would work best for that. The engraving supply
places sell only very thin stuff, so I will be getting
it from an aircraft supply house. They are the only
ones I found that sell it with the protective plastic
sheet over it. All the other places I have bought
my aluminum from give me a piece all scratched
up that requires an hours worth of sanding. I will
be using a floating engraving head with a 1/8"
cutter at about 15,000 rpm

Thanks, Bill