500 feet is an absurd height from which to abort a PFL. Everything can happen between 500 feet and the ground. 500 feet is my average circuit height and if I chop the power on downwind I do not hesitate to admit that I don't get it in every single time without a little 'engine warming' or else some sideslip with full flap.
50-100 feet is an appropriate height to go around.
QDM