I think the most fascinating thing is what those big blues eat. Steve Coulter of the Sea Creature told me he figured the a 20-30lb YFT or 30-40lb mahi was probably the best bait to get a 400lber to look at you. Ive seen them bridle some football sized tuna and things up for those blacks out in the Pacific, and kings and spanish in the atlantic for blues, but not sure how you'd fish a 30lb YFT or 40lb dolphin lol. I do recall a story out of oregon inlet, guy had a bull dolphin almost to the gaff and a 350-400lb blue engulfed, and swallowed (not sure if the hook got lodge or what) to the point where they were able to land the blue as well.
Also read some things where a 100lb+ YFT was found inside of a grander+ caught in hawaii, as well as some white marlin and spearfish found in some of the large fish.