In answer to your question regarding the overcured boards, you need 
to be concerned also with the adhesion of the solder mask and 
breakdown of the solder mask.  Regarding the laminate, an increased 
cure should not affect any of the electrical properties you mentioned.
  Copper peel strength could be degraded, and flex strength of the 
laminate will be affected.

The fire retarding properties will not be affected because the fire 
retarding properties come from inert ingredients added to the resin.  
There is a covalent bond between these ingredients which will not be 
broke by over-curing.

David Mander
Sun Coast Supply
Longwood, FL
800-264-1250
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