On behalf of your moderator team - I'd like to suggest that no one alter a boarding pass to avoid the dreaded SSSS.
As has been posted in a few threads - your SSSS boarding pass must still be marked prior to boarding your flight (per TSA rules). Marking your own boarding pass is clearly not how the system is intended to work - and will probably be considered a crime.
Some friendly words of warning! I'd hate to see any of our valuable FTers find themselves in court - or on a no-fly list!
-Chris
TS&S Moderator