http://arrowskp.com.
Read what Kelly has to say about tuning. It seems oversimple compared to a lot of the information we're used to - but it has worked as well, or better, for me, than overthinking it. Don't skip reading what he says about broadhead tuning, too.
Kelly is no longer in business (as he describes on the webpage), but has generously offered some of his knowledge. He's not selling anything, so he's not competing with our sponsors (who I do buy from). Just a reference.
As I understand it, he is VERY well respected by those who dealt with him while he was active. Just have a read, and a look at his spine chart, and see what you think.