I noticed watching Age of Ultron, when the Hulk and Tony are fighting, that the Hulkbuster suit is much bigger than Tony is.
Obviously in the regular Iron Man suits it fits around his arms and legs and he can move them around using his own limbs.
But from the size of the Hulkbuster suit he must surely only fit inside the torso of the suit.
In Avengers 2
when the Hulk shoves a lamppost through the shoulder of the Hulkbuster suit, the fact that Tony doesn't lose his arm/hand shows that his limbs definitely don't reach that far.
So how does Tony control such a massive suit? It shows the Hulkbuster suit covering his regular suit, so is the smaller inner suit like some sort of controller for the larger outer suit?
I would say maybe the torso is hollow and he's moving around in there and the outer suit is following his movements (Real Steel style), but from the hits he receives from the Hulk the torso would surely cave in if it was hollow.
Is it ever explained in the comics? If not, does anyone have a speculative answer?