You should probably try the hickory first. If you cut it now it is going to be very hard to get the bark off. If you wait till May or June the bark will peel right off and the first ring under the bark can be the back of your bow. If you peel the bark and work it down to 2"wide by about 1.5" thick and set it in your house somewhere it will be ready to tiller in about a month or so. Might should clamp it down to something to keep it from warping. The closer you get your roughed out dimensions to the final size of your bow the quicker it will dry. If you try to tiller it before it is dry enough it will take a lot of set.