Actually I got the following from a buddy who has one:
I know what you mean about the trigger pull! If you want to make it a bit better you can stone the sears a bit, but the big thing is take the bolt apart and cut about 1-1.5 coils off thespring,go a little at a time .It seems when they made these they put in and really strong spring [too strong] and many of this little guns have been buggered because people kept stoning the sear trying to make the trigger pull better .
Mine had been stoned to the point where if you handle it fast it would pass the trigger sear and go to the fired condition when you closed the bolt[it never fires just goes to the uncocked condition],and my trigger was still very heavy .I read up on the problem a bit and that seems to be the cure .