Probably means triple by weight, not cubic inches--ISTR that fuel capacity and internal vehicle capacity were two of the main drivers in hull morphology, while maintaining a deck footprint no greater than an Echo.
I'll bet there's a lot beefier backbone carrying the drivelines and transmission for one... haven't seen anything about the rotor but I'd expect changes there. (Personally, I'd have gone up to an 8- or 9-blade rotor along with new blade technologies, allowing "headroom" for engine growth or development into a 4-engine superheavy-lifter variant, but then again I AM from the school of Nothing Begets Success Like EXCESS.)