How can you set the width and height of the projector file after you have published it, So that it is non scalable?

What i'm trying to do is make the projector non scalable and always opens up in the middle of the screen. How can this be done? I have tried the fscommand but i can only get the projector to open up the file at "full screen".

I have heard that you might be able to do this with the xyz cordinates, but i do not know how i can use this formula stuff?

any ideas?

Any help would be grateful. many thanks in advance for your time and effort!