My saddle is as far back as possible while keeping my thighs from hitting my chest in a full aero tuck.

There is nothing magical about the 3:00 pedal position. Basically all you are doing is rotating your body around your crank. If you are bent over very far like in a TT position with your back literally horizontal, your saddle should be forward enough to keep your thighs from hitting your chest, which might bring your knee forward of the pedal in the 3:00 position. In a more classic road cycling position, your saddle should be further back, putting your knee directly over or behind the pedal.