In a previous article, David Megginson said:
One of the major recommendations is that the only time a pilot should
fly at (rather than above) a minimum IFR altitude is MDA when weather
conditions require; otherwise, leave a healthy safety margin. Of
course, you'll have a hard time convincing a flight test examiner of
this, but in real life, it makes sense to me -- my plane is a lot
slower and can descend at a lot steeper angle than a big airliner, so
I don't need a long, shallow approach slope anyway.

I don't know if this would be considered "a healthy safety margin", but my
examiner said the same thing that my instructor did - that the PTS says
+100 feet/-0 feet, so you should always fly 50 feet high to give yourself
a bit of a buffer.


--
Paul Tomblin http://xcski.com/blogs/pt/
Pascal - A programming language named after a man who would turn over in his
grave if he knew about it.