partially off the window quads

Ok I drew three quads in the center of screen the middle quad had 0 for al it Z value. The one on left has a Z value for its left side of 2 but its right Z coords are 0.
This all look great when in center of screen but when I move the initial draw from point over so I can draw in an exact x,y position half of the left image goes off screen as I wanted, but the darn thing is no longer at the correct angle from the center on. It seems to have shrunk the image somwhat. Could anyone explain why this could be happening?
My proggy pretty much draws the back of a box the left and right side at about 45 degree perspective.