Any homogeneous material will work, if it's relatively new.
Arrows will follow the path of least resistance and even in foam, if there are prior channels from prior arrow shots, the nock will end up pointed wherever it stops after hitting a corridor.
Gery, the EFOC doesn't work as well for the Bare shaft planning method. I used that for years myself...
Other reality is that a pro arrow builder who sold to competitors found that even the most expensive carbons have variance, usually in spine, in a given dozen. Actually 2-3 per dozen that were out of spec.
Friend told me something I've seen in videos...that the high (stiff) spine side can make huge difference in spine of a given carbon arrow... or wood...
The machines of the Carbon mfgs just roll em in any which way which may equate to why there is variance when hand spined...
I'm buildin a cheap spine tester and fletch cock feather on the stiff side of every one here on out.