I have made 2 elm sapling bows with diameters about what you are describing. They were both made for the MOJam hatchet bow contest and both still shoot even 10 years later.
Cut it to 70" and peel the bark. Start working the belly side flat. Get the limbs less than 3/4" thick but don't narrow it and keep the handle area the full size of the sapling. Let it dry for a week and then lay out a bow 2" or so wide for half the limb tapering to 1/2" at the tips.
BTW, if you carefully slice the bark into 1" strips before peeling, you can weave a cool basket quiver with it. Just bend some limbs into a form and weave the strips through it. Take a couple pinky sized limbs and straighten them for arrows and you can have most of a hunting setup from one little tree.
I did this years ago on a weekend camping trip with my oldest daughter. I used to have pics on my old website. I'll see if I can repost them on my new site. I also made a walking staff from the same tree. The leaves became bedding and we burned the rest of it.