Wait til after you go to the seminar to make a decision. Take a ride to CMS in New Bedford some day when Erik is working. Bring the reels, ask questions, get line spooled, buy stuff. thank him. Easy
They know Tuna there and can be very helpful.
I would think for small tuna, you would want backing made of braid, then heavy enough mono, then flouro leader. But before you go setting that up for those tuna in the fall, you could set it up as backup for trolling even though it is a bigger reel than neccessary.