Word down in the fuel shack the other day, confirms what you are saying. The plug/stab mod's are an attempt to correct problems with pitch stability on the aircraft.
All the Sikorsky designs with this style of tail cone/pylon seem to have experienced structural problems over the years; S61R, S64, S76. You'd think they might have resolved some of htis by now, but then again, maybe all the old guys have retired?
I'll find out what the janitor know's next!
