Then it happened... a REAL engine out.  So, I too went in "Done this before" mode.  To my surprise, the plane sank MUCH faster than with the engine at idle (as in practice).  I felt betrayed... LIED to by my instructors.  Anyway, as soon as I realized what was happening, I made a bee line for the numbers and all turned out fine.  Subsequently, I learned about the flat plate drag of a windmilling prop and ever since, I never get too far from the runway in the pattern and I'll always be sure to have a height buffer if/when it happens again.  I figure I'd rather make the runway and land too fast than the alternative.