[Rodger Knox]

Yes, what I show in the photos is way too heavy for an acoustic, it was designed to play electric without feedback. I'd go with spruce for the top, about 1/8" thick, and whatever hardwood strikes you fancy for the rest. The sides can be pretty thick, 3/8" to 1/2"(that will be thick enough that you won't need linings to glue on the top and back), but I'd go about 1/8" thick for the back. As for the size of the box, 12"to 15" wide, 18"to 20" long, and 3"to 4" deep. You may need some bracing for the top, that depends on how big you make the box. You don't need laminate, solid wood would be better. You do need a way to thin it down to the desired thickness. What kind of tools do you have?

It would be easier to find a neck you can use, and build the box to fit the neck. That's what I did for the 12 string. Building a neck isn't really that hard, but it is a bit intimidating, and takes some time. You will also want to use a typical acoustic bridge, without the block underneath as shown in the photo.