andrewebay1They all are pretty flexible. I have a big head myself and use a model similar to the PPK, but their metal frames all generally follow the same construction principles so you shouldn't have an issue. Probably would not recommend Intercept as I've yet to wear a pair of any glasses that style and have them fit comfortably.
CyphreI have a big head myself and was surprised how comfortable the Intercepts were for me. Only tried them even because I was at PAX and the rep said "no I think it'll fit". For reference, I bow out the temples on the Vayper and RPG just because of the width of my head, and at least half of the glasses/sunglasses I see in stores (clearly meant to fit most) are unusably narrow for me.