Hi Calvin,

   Stick with 8 strings if you can. I know, a lot of folks think 8 strings causes too much tension.  The one I built has no bracing in it. Instead, I used a sound post. I didn't even put any kerfing in it. It sounds great and still holding together. I was playing it one day and my wife thought I was playing my Gibson. I suggest using a box about 12" long x 10" wide and about 2" thick. Solid wood. Repair any cracks before you start. However, I suggest that you glue the box together. Unless you use a lot of bracing, forget about leaving it so you can open it up as a lot of makers do. Yes there is stress from the strings, but the box can handle it if its glued solid. Double strings give you double the volume. Using 4 string means you have a uke in fiddle tune. My opinion. And you know what they say about opinions. Oh well. Good luck. Craig