There's a good thread on pbreview about this, I was working on mine just today.
What I did, to reduce the travel needed to drop the sear was put a sleeve over the pin that the sear rests on, thus raising it at one end and lowering it at the business end (as its on a pivot).
The cunning bit is that I just had to use a cheap ball point pen: a paper mate 2000 stick med.
I snapped off the end of it, and it fit nice and snugly in the frame. Then I made a backstop like Paul_collier said. All it needs now is a front stop of some kind