I used 1/8" It takes to the curves well, and most any "real yard" will have it, or can get it easily! For underlayment, ask for door skins, a luan ply, 1/8" thick. For finished surfaces, I agree with Doug, use birch. It takes a finish nicely, and will lighten up the interior..if you like that look, of course!

On soapbox!!.
I think that if we, as builders/hobbiests, don't support the smaller yards, we'll see them go away into history, along with the drive-in, local butcher, pharmacy, etc. (Insert Happy Days Theme Here!) I find that the locally owned yard will be really responsive, and usually competitive. At least my guy is!
Besides, most will agree that the box store's quality has declined, and selection is poor. They just sell you what is best for them, not the best product.
End Speech!!
