If the input beam out of the aspheric collimator was perfectly parallel then the cylinder pair could be placed anywhere with the same 2:1 magnification. But, because the reds diverge so quickly, even when collimated, then the further the first (negative) lens is placed from the diode the more powerful the resulting divergence out of this negative lens, This is because the beam is intercepting the glass over a larger diameter and this means the more steeply curved glass is being utilized. Another way of saying this is that the lens will be acting at a shorter F ratio.