I sell POC and Douglass Fir and I've shot both of them, along with pine, chundoo, laminated birch, poplar, hickory, and others I can't remember.  Any supplier can get you just as tight a group of shafts as you would like if you call them and talk to them.  Currently we are pretty low on the 70+ spines because the suppliers just don't make as many, but they are available.  Cedar is the straightness king in my book.  I can work with Douglas Fir but POC is still my first choice.