Sorry sushi, After replying to your post I re-read it and I realized you were answering my question.
so for an example: if I have a projector that is supposed to be placed 12' from a screen for front projection and I wanted to rear project it using a mirror the distance from the mirror to the screen would be roughly 6' ??

anyways thanks for listening to me bable, like it says next to my name, NEWBIE :-)

timmy