I'd like to make a rosewood or ebony pickguard for my archtop. I see rosewood in 2mm thickness for a reasonable price. Does anyone have experience with wooden floating pickguards? I've only seen pictures (like Benedettos), but they look great.
This will depend on the quality of the wood, your skill in finishing it, lacquer used, direction of grain, as well as your mounting mechanism and your playing technique.
Remember, depending on how you fix it, you may have interesting stress points through it, and not just when you strike it.
Personally I'd be happy with 2mm, if I ensured a truly flat mounting, and was only going to use the guitar for fingerpicking or classical styles. I get a bit rough sometimes with a pick and I don't think that thickness of wood would cope.
If you are in doubt, you could always try a thicker piece, and just sand the edges down thinner - it will look the same.