Bob, in your quote, when you roll up the piece of paper, where the two edges overlap is the spine. It makes sense that it is more difficult to flex the paper with the overlap/spine on top, as it is thicker so it should be more resistant to flexing. Same theory applies to arrow shafts, golf shafts, fishing poles...

That clears up a lot for me.

So the deflection or flex of an arrow that we measure with the two pound weights is just that, a measurement. But the spine is the stiffest point of deflection running lengthwise on the shaft when rotating the shaft 360 degrees. What the easton chart measures is deflection then correct, and finding the correct spine on an aluminum is not that necessary because the shaft is so uniform.

I have always understood the whole concept of matching spines on cedar arrows, but the language seems very interchangable these days.

Rangeball, thanks I understand what you are saying.

But then, one question, wouldn' t a spine tester (maybe named wrong, should be deflection tester) actually help in determining where the spine is, especially on a cedar arrow?

Sure, a spine tester will identify where the spine is located, as well as the deflection/flex of your arrow. Two jobs for the price of one