I decided to go with a cross bracing because by all accounts it is best suited to the single sound hole, provides good rigidity and brightness, and plays in rapidly.

I used straight-grained pine for the braces as this seemed to be closest to bass wood that I had in my shop at the time. I thinned the tops of the braces and cut a cross halving joint to connect the intersection. I also added a brace next to the sound hole for extra rigidity and glued them in place with hide glue. I used that glue because it is acoustically transparent – it doesn’t interfere with the sound.

I tapped the top and reduced the braces to achieve a tuned plate at G, reasoning that this would give a good bass response.

Here is the bracing pattern. I may add another brace at a later point if it needs it for structure

mandolin cross bracing