Well, above 500' I've gotten away with it several times. Used to practice this regularly in 152s and 172s, throttling smoothly back to idle. Sometimes we would land, sometimes we would see that this was not possible today -- go around! After doing this some tens of times you kind of get a gut feeling about how it will work out. I say, better to have tried it knowingly and with an out, than to find out in dire straits...