1 blade's pulley is 2-3 inches in front of the other blade so that they can overlap. If the grass is not stiff, meaning a bit wilty from drought or lack of water, there will be a strip in the middle. Sometimes, tall weeds don't get knocked down if they are ran over near the edges. I guess these decks just don't have that good of a "vacuum" effect like a good ole Snapper Hi-Vac single blade. I have a gravel road and am constantly having to sharpen my blades from hitting or sucking up gravel rocks.
My deck might be a 42" "Edge", is that the same as you are talking about?