What you shuold start off with doing, if you didn't already that is, is use that screw to adjust the length of the pull. On older ones you'll have to take the frame off to adjust it, on the new ones you just poke your hex key into the screw at the top of the trigger and turn it. You'll want it almost touching the switch- just far enough away to be reliable.
For actually 'lighter' you might look at the magnet mod- it replaces the trigger spring with a set of magnets. It should be in the sypder sticky threads, if not look at the source: Otter.
http://www.ottersccustoms.com/ his site is great for spyder tips and tricks.
Does your imagine have the flat 'blade' trigger or the standard double curvy one? Some people prefer the feel of one over the other, that's one of the biggest reasons to get a new trigger.