Ive made more than a few 26" draw 50# yew bows, and you can get that with not alot of wood. As you said 1 1/4" to 3/8"s 60" would do the trick.
you could shorter if you make it bend through the handle, but if you havent made many bows, or if you want to UP your chances of it becoming a bow, leave it full length.
If my sapwood is 3/8" or more I thin it, and violate freely. Just make sure you sand it baby smooth, take down your corners, and it doesnt hurt to burnish the back too.
As stated, yew deflex is tough to get it. I just roll with it, and usually recurve the tips.