I don't see that. Harding was tough as nails, and Froch has never really stopped a durable fighter. Only Taylor, and Bute, who are both fragile.
Could go either way... I figure Froch's a light heavy in the 1980s sense anyway so there's not really any question about size adjustments Froch's best bet is to jab in his weird way and minimize the exchanges and rough stuff... For Harding, as always, the best bet is to brawl... The more of a brawl, the more I like Harding's chances