You can be a little more flexible with hickory than red oak. A plain sawn board works as well as a quartersawn.
Your bow looks great, much better than my first! As for the tiller, FYI, if it bends evenly on the tree when supported and pulled from center, the lower limb is gonna bend more when you draw it in the hand (hence the previous discussion about positive tiller). If you look back at all of Roy's pics, you can see he allows for this by placing the support for the grip where the hand would apply the pressure, and he has the pulley hook draw the bow from above center. There are lots of ways to go about it, but you will want to make that correction on your next one.
Best of luck with finding some hickory (some stores market it as pecan, most sell pecan AND hickory as "hickory"). Ash would be good too, or white oak. Some round here think white oak is better than hickry.