I only shot tapered arrows, even though can't really see the difference with my recurve, with longbow hawever they're much better than parallel shafts;
I would start with parallel cedars, lets say 23/64 and 70-74 spine, get tham really straight, than I would put stain on the nock end of the shaft (7"or so)
using small block plane, I would taper the shaft to make stain dissappear,
instead of calipers, I controll the thickness of the shaft with guides for Tru-Center taper tool
I would finish with 80-100-150-220 sandpaper and #00-0000 steal wool
from my experience shaft looses about 2-3# of spine, but that's ok (You can use lighter point, without altering FOC much)
entire arrow will be about 20-30grains lighter, than parallel shaft from the same set and will fly like a dart