Right, I thought that you had the fours on the back!!! However, It still applies. The rear caliper is at the top and the bleed nipple is facing forwards(or backwards) and is not at the top so the air can sit higher than the nipple, therefore the pedal is always going to be spongy, thats why they need to be bled with the nipple at the top.
However it all depends on what you've done to the system as if you've only changed the fronts, then there should'nt really be air that far back!!