I built a vine maple bow last year....first one I ever did, and it came out great. Killed a decent buck and filled an antlerless tag with it. Easy to work, and very resilient wood. My wood was probably quite a bit drier than your, due to where I live, and the fact that I'd had the stave for some time - years.
My "back" was the wood just below the bark, and came from a larger diameter tree than yours, perhaps 4 inches or so. Do a search for vine maple in the threads, and you'll get a few good ideas and input, from some who've built many of these bows. I have to say, as an osage enthusiast, I was quite impressed with vine maple.
Seems like you have quite a bit of length in the piece you have. I would not de-crown, but would build it a bit longer because of the narrow diameter. I've seen Strunk build some impressive limb bows from narrow limbs of serviceberry, without decrowning. Not much more I can offer up. Just go for it!