If you want to play it safe back it with rawhide. Yew is great, very light but it has a reputation of increasing draw weight and suddenly breaking when its cold, and dry. I have read about this in old issues of Prim Archer.
It seemed to be more of a factor with narrow limbed elb. You could also make the limbs a couple of inches longer than your usual design, so it is under less stress, if you go into harsh conditions.
If it is going to be a hunting bow I would always back a yew bow to stop the sapwood getting dinged.
Hamish.