Looking at your bows, it is difficult for me to tell what type of spine you need. That's probably a bow dependant issue anyway. Still, I'm not sure why the tail would be flying high if it's not a problem of nock placement. However, I only shoot wood arrows, so I might be missing something here. Is your longbow a high-performer (how radical is the deflex, etc.), what's the brace height? Sometimes my arrows fly nock end down if my bracing height is too low.

Somebody else can probably help you better than I can.