I have the spring fitted also but you still get a floppy pedal, all you can do is adjust the adjuster bolt to take up the slack/play.
I think its because there is no longer a ratchet mechanism to self adjust, everything will always feel a little floppy becaue until you depress the pedal the cable is loose and the ratchet has nothing to engage its teeth into (which is why the spring doesnt do anything anymore).