If da stem ist cut too long, da pilot shaft will "bottom out" against the main plate (or da retaining groove against da set lever stud when it reaches da end of its travel). In either case da crown gasket will not be fully compressed irrespective of how "tight" da lever action ist. For dis reason, da lever tension ist always checked with da movement removed.
How does your current water resistance compare to it's pre modification level?
stiff muckler ist im da Haus!
p.s. long stem = broken stem or wet uhren