I noticed something interesting last week while playing hooky. Every eye I caught was while trolling 3-4MPH on the GPS. It started while making a tight turn with both lines out and I sped up. Bam a 15-1/8″ hit on the turn. So I kicked up the speed and it seemed to help. I managed triplet eyes all just over 15″ longlining cranks. I also picked up a 14″ in the same area.
I learned something else too. I set my drag just heavy enough to keep the drag from slipping while trolling with super line. I figured this out after losing my first 2 fish 
Hope this helps,
Ferny.