Something else you might like to consider doing for an English longbow of the period, if made from native yew it could be knotty, which apparently wasn't too uncommon:
http://heartandsoil.blogspot.com/2011/06/my-yew-longbow-in-detail-chris-boyton.html
More good photos of nocks in the above link.
Einion
That's an interesting info. It contradicts what I once heard in a conference paper about English longbows. The author insisted that proper bow could only be made from trunk of fully grown tree and it has to be knot free. In fact, he claimed that from one trunk good bowyer would be able to produce 1-3 good bows (made from side facing south*), few more of medium quality and the rest will be only training/hunting class. Obviously we have to take into account he probably meant extremely powerful examples, as some were up to 80-100 kg draw.
* or north, I don't remember. Either it needed to be from the side facing sun or not, as each gives differently grown fibres.