Hi Mark,
I have the Stealth 78HH and Stella 14000SWB combo loaded with 65lb JB solid, which I bought it for use mainly with poppers for larger kings and tuna to compliment my Saltiga S-Extreme 80TN that I use for the same species with sliders and stickbaits.
I am yet to use the 78HH in anger, however it is a deceptively powerful rod and fairly stiff too, that's why I bought it for poppers, though in saying that it will still fish larger scale stickbaits in the say in the 120-130gm or so range.
It would be a perfect match if you want to use it for mid range GT's or larger tuna and other species, if you search around, there are a few videos around showing the STK78HH in action.
Hopefully there are some guys around with real world use on this model that can chime in to let you know exactly how it fishes.
All the best,
Cheers,
Ian