Summary

To save time and filament, print these with:

0.8 walls (2 perimeters, or 2 0.4mm walls)
4 bottom or top layers
0.24 or 0.28 layer height (assuming a 0.4 nozzle)
0% infill
Speed and temp are up to you depending on your filament

Printing them stacked? Give them a generous brim such as 8mm or a raft of equal footing. Once you get brave and stack them a bit high - say 10-12 or more, then maybe enable z hop to avoid potentially knocking them loose. Your slicer should be able to just add new_visor.stl on top of one another. Watch the video below for the easy way to do a quick stack in Cura. Other slicers will do it just fine.

If your printer or slicer doesn't like a 0.2mm space between them or even a 0.05mm space between them, try stackable.stl and leave a space of 0.2mm. There is support there to string them together with the right settings. Not as easy to get apart however.

Once printed, a razor blade held with some pliers that is warmed up with a heat gun makes quick work of the separation if they dont prise apart.

This is a great 3 minute video showing how to stack:

https://www.youtube.com/watch?v=lfSRpG20FmE