Just a quick check Tagan, but unless you have your astral construct up and set to trip, you won't be able to make a trip attack during a regular AoO.  (though I'm allowing you a readied action to get the attack off anyway)   That rule is important for keeping the spiked chain fighter from being excessively silly.  (though the trip extraordinary ability is another hole in the system that makes the trouble happen all over again)