Saw this video for the first time tonight, perhaps some of you have seen it before. There were a couple of interesting points. One is that he builds blanks so the spine will be on the top when then rod is held out over the water. So for a casting rod the guides are on the spine and for spinning and fly rods they are opposite.
Secondly is the comment as they transition from finding the spine to assembling the handle he indicates that if you hold the blank so that the spine faces up you'll see a gentle up-curve, I'm wondering if others have found this to be true? I'll have to check it next time I have a blank on hand. But it seems to follow that, unless a blank has multiple curves in it, the straightest axis, when the curve goes up or down rather than to the sides, will give you guides on either the spine or opposite the spine.