I wouldn't try and radius any fret boards that thin, you won't have any fretboard on the sides. And I hope they're true, not much material to finish sand if you need to.
Fret boards do more than just hold the frets, they had strength to the neck, and when you fret a string, the fret acts as the nut and from what I've read, it contributes to the sound as well.
Not that thin fret boards haven't been done, just not widely advised from what I've read over the years.
they would however make great box building material if you make your own.
Hi Scotty, yes as Richard says, plus the fingerboard adds mass to the neck, which on a CBG 3 stringer would not normally have a truss rod fitted, so would help keep the neck flat. Mass in the neck can help create more sustain from the strings in the body.
For a good buzz free fingerboard its good to start with a very flat f/board before fretting, thicker stock allows for any reworking needed in this regard.
If your neck is stiff and straight a 1/8 f/board would work, but I would suggest slotting and fretting it after gluing to the neck. I also find that the 1/4 f/b gives me a better bridge height.
Fretless slide, glue-on-top frets like tooth picks, bobby pins, cotter pins, zip ties, or glue another 1/8 in different wood to the underside for fret slot cutting and a neat color contrast.
My vote is for the walnut
You see fender guitars with no separate fret board, So the thickness, 1/8", in and of itself should not be a problem if it is pre glued to the neck. Just make he rest of the neck thicker.
On one of my builds, the neck will be just under the top. My fretboard will cover part of the box top so I was looking at either cutting back some of the fretboard thickness to transition to the box top(1/4" to 1/8") or cutting through the top and risk leaving a noticeable gap around the fretboard. None of the hardware lumber centers had 1/8" thick wood pieces other than Plywood, so I'm going to check some of the hobby stores for some suitable 1/8" wood to put between the fretboard and neck from the box to the nut. Thanks for giving me the idea.
Doesn't matter how long or how short of a time you've been building guitars, there's something you can learn or find a new option/way of doing things everyday. If you can't learn anymore, it's because your not willing too.