Here is on of many STC's for windshields and there is no Vne limit listed,
Supplemental Type Certificate
The STC pre dates the Sikorsky letter. Which is not a ammendment to the flight manual,
There is no Vne listed in any of the windshield replacement STC's for the S-76 or any other of the STC's for door or chin bubbles.
Just about every installed piece of equipment is a STCed item on the S-76
There is no FAA Ops Manual that has anything about windshields in it.
Plastic windshields are the norm for most of the helicopters flying in the world I do not see that changing.
Fatal Birdstrikes to aircraft are rare, plastic or glass windshields they will and have come thru both on a S-76.
Its more dangerous driving to work down here in the Bayou than flying offshore.