You know, I’m not sure. I do have some aluminum settings saved as a custom setting, but I don’t remember the exact numbers. Given that this is a non-proofgrade material, discussing the specific settings here would make it so we have to move this topic to beyond the manual and I’d rather keep it here in made on a Glowforge.
That being said there is a post that can help you find recommended settings for every model of Glowforge. Check out number six in the FAQ, here is the direct link:
That page covers testing processes and also has links to spreadsheets of suggested settings to get started. One thing that I found is interesting is that different colors of tags have slightly different sweet spots to get a consistent white engrave. For example I found that black took more power than gold with my specific batch of tags. A little bit of testing is probably a good idea.