The shim thing as described above worked for me many moons ago...
Also, if you don't want to mess with the rifle basix sear kit, you can always just replace the sear spring with a Pentech Mechanical Pencil spring (they happen to fit perfectly, well tried and true if you surf many of the marlin forums on the net)...ancient marlin trigger trick, works like a charm! It lowers the trigger a great amount, but not too much, and costs about......a buck fifty if you get one of the spendy mechanical pencils.