I have worked with wild plum in non bow applivcations....whistles, flyboxes etc. When that stuff seasons it is rock hard! the colors fade somewhat, but it glows with tung oil, very rich. I have had wrsit thick branches check pretty badly, but think for a stave I would season much more carefully. My only surviving wild plum tree looks like an overgrown bonsai, not on remotly straight branch on the thing. I'm going to cut some suckers of with part of the root and transplant them to other spots in the yard, crowded with other plants so they'll grow straight!
I can't wait to see it....I hope to build a plum bow in the next few years (once I actually learn to make a bow!).