That doesn't look too bad to me. Yew is very forgiving, I've doen some very 'bad' things to awful Yew just to see how far I could push it, see 'Mr Wobbly' on my website if you want to see a bad knot.
You can get to my Bowyers Blog from the website, and I did a short Yew primitive in June which is blogged up on there, which may be of interest, it has a good sequence of tillering pics. (or google 'Bowyers Diary')
It would be nice to see a side view so we can see how much heart/sap wood you have.
Del
(BTW, With a long sting, you still want it as short a s possible (E.G Just long enough to slip onto the stave.) Else you get a very false impression of poundage early on.