I fished with these reels off the Kona coast for grander Blue Marlin. Reels loaded with hollow core dacron with finger trap connection to 200 yards of IGFA class 130# Sufix Key line. We were using big live Bonita as baits.
I think there are no finer big game reels made. I thought that Old Salt has gone to one of these reels for big shore based sharks.
We used some 25-ft 500# mono wind-on leaders pre-rigged with a 600# Aussie style snap swivel. This wind-on was attached loop to loop with a bimini loop in the 130# line. We would connect at this snap our live bait rigs that we pitched back after bridling the hook on to the big live bonita bait. We would bridle on the live bait drop it back in the tuna tube and hook up to the 600# snap. We we were ready we would then drop the bait back in the spread.
I've used the rig that you mention when I worked as deckie on a boat in Madeira. The only difference was that instead of a Coastlock snap they tend to use a stainless steel shackle to join the short lure leader to the main wind on (I've attached a picture). They don't use livebaits in Madeira preferring to cover more water by fast trolling with lures. I've live baited with big (10 - 15 lb)skipjack tuna in Mauritius and it's a very successful technique. They take blue and black marlin, hammerhead & mako sharks and BIG yellowfin tuna (only the really big ones can eat a bait that big!). I took a 450 lb blue marlin and a 400 lb hammerhead on the same day with livebait.
I haven't fished for the big bluefin before but I'm told that they're very shy of any hardware near to the lure so I think long fluorocarbon leaders may be required.