For good osage, 1 /5/8" wide to mid limb is plenty. We made a bunch of 58" bows for 60# @ 28" in '06 and '07 for another magazine "challenge." It was a challenge, and really opened my eyes to what is possible w/ osage. All of mine where stiff handled. One I used deflex in the glue up and small recurves. Another was full compass tillered. Another more stiff on the outer limbs.
Based upon that experience, I reckon I made 4 or 5 of these, 61" would be fine for 29" draw. Some folks prefer recurves, or bendy handles, to combat finger pinch and string angle. I prefer stiff handled, straight limbed bows and have the bow bend mostly on the inner limb, leaving the outer 1/3rd or so stiff and narrow.
It's tricky when you push the envelope like this. You need good material, preferably without knots or features in the working area, good rings, moisture control, all the fundamental stuff. But if you've made a few bows and have sound technique it should not be a problem. Just take your time and let the wood guide you, like any other wood bow project.
Not discounting any of the suggestions already offered. In fact, I think the examples in the challenge revealed any number of designs could be effective.