viking: I'm familiar with using a spiner to find the stiffest orientation and affixing the nock accordingly, but I don't use that method.
The strongest orientation of the grain is perpendicular to the bow side plate, IMO, regardless of whether that's the highest orientation for the spine, though it is usually that, too.
Not a big difference, regardless, usually 3# or less. I go with strength rather than exactly matched spine, if I have to make that decision. Keep in mind, too, that most suppliers spine perpendicular to the grain so that's usually the most consistent measurement across a number of shafts, and, of course, it's the way to go if one doesn't own a spine tester.
Rifleman: You should be able to adjust your clamp to give you the feather clearance you want so you don't have to fiddle adjusting the nocks after fletching. Good luck.