^^^ Ah, that was my next guess, that you reposition your feet. Not necessarily a bad idea, since the position of a clipless shoe's cleat can affect leverage, too.

Keep in mind that your effort to keep your feet on your pedals during the whole stroke also works against you. As you're pushing down in front, you also end up pushing against your rear foot, so some of your energy is spent pushing against your leg instead of the chain.

If you aren't already, think of scraping mud off your shoes at the top & bottom of the stroke the next time you're riding clipless. You can kinda do this on platforms, but it really is easier on clipless (even easier than toeclips & straps, IMO, because you'd have to cinch down the straps pretty tight to keep from pulling your foot back-and-out at the bottom).