say, fiberglass shooty stick chef boy, what the heck you need one of them manly tools for, you are just liable to hurt yourself. if you are wanting to upgrade to a stickbow- you prolly could find one for a few $ on the auction site.
seriously- they are the greatest little tool ever- but really dont work on a squigly staves- if you are trying some of that old english yew- but they are a winner on board bows etc- which if one is learning to tiller- is a good place to start- a nice consistant , straight piece of wood.
dont be stressed- tillering is not that tough, if a one eyed 'ol fool like me can build an ok bow- you will do just fine.