X brace CBU?

Hello, I have a cigar box ukulele that I bought on Etsy a while back that is bowing at the top. I plan to put in an X brace to see if that helps. I am not a luthier but will give this a shot. If I totally screw it up I have more cigar boxes and anyways will learn something from the process either way. What type of wood should I use? Since this is just a cigar box with a threaded bolt for a bridge, would a cut-down paint stick stirrer work? Does anyone have any other suggestions besides an X brace? I have plenty of other, "real" ukuleles. This is just a project to learn from. Here's a pic:

I'm not a building expert but the first thing I would suggest is that there is nothing showing in that picture that shows a need to do anything. In the world of ukuleles any top that doesn't bow a fraction either through time or deliberate construction is overbuilt.

Some of the best builders here will deliberately have a slight dome top on their instruments. Any top that is built flat but doesn't bow one way or another slightly is just too heavy to be a great instrument. I have a bunch of ukuleles that I checked for flatness a while ago and the only one that was even close to being dead flat was WAY too thick in the top to the point that no bass frequencies were getting through.

Anthony

Well upon reviewing my previous messages with the builder it may be more of a situation with the neck joint settling in than the top itself. It plays well enough, but none of my other ukes (CBU or traditional) seem to exhibit this degree of bowing. Not sure if this is something I want to attempt to tackle on my own. I may end up contacting the builder again, although it's been several months since it was purchased.

Looks like the neck is indeed rotating. Contact the builder, as it's something they would want to know, so as to lessen the odds of it happening to other instruments.

Status update: All Fixed!!! I sent it back to the builder. He said that "the top had cracked on the inside right down the middle, to the extent that the brace across the middle had popped loose on one side. I disassembled the uke so that I could glue and clamp the crack and replaced the one brace with three to stiffen up the top a bit. I replaced the neck mounting block with a beefier one and re-attached the neck with an additional screw to increase stability." And sent it back to me promptly. Very pleased with the results!