There are two different types of spine. True/actual spine of the shaft and dynamic arrow spine which is how the finished arrow acts when shot through a specific bow. Why do I say specific? because a single arrow will shoot differently from different bows even rated at the same poundage. yade, yade yade,
Boy I'm getting wordy........
Actually, to answer your question....yes, it effects the flight path of the arrow. Their is a lot of variables for good arrow flight if you look at it technically. But lately, for a 50#-28" draw bow (typical) all I've have been doing is cutting some cane using a 3/8" open wrench as a gage for the big end thickness, making some arrows about 32" lg with 16 penny duplex nail as points and 3 feathers 5" lg for fletching and they have been flying great!!!
You can read all you want about making good arrows but the best way to learn is to make some. I have made hundreds of arrows some good, some bad.
Have fun and make some arra's ............... let us know how is going.
Till next time,
DBar