there are really 3 bivy sites on the ridge - 1 at the base, 1 at the notch and the summit (though there's one at the base of the gendarme too i think, but i'm pretty certain a tent won't fit there?)
you can do the i-ten at the first and last in my list for certain, and probably at the notch too, though i'd recommend just a 32 degree bag and some tyvek and that's it. my last time bivy'ing there i had just a bivy sack and down jacket and thought it too cold - a bag and nothign else oughta be fine, good weather permitting.