I've learned a bit more about MYLAR...
Apparently in the manufacturing of Mylar films they are heat-set to stabilize them as the last step. They will then exhibit no more than the specified amount of shrinkage as stated in the data specification sheets UNTIL exposed to the original heat-set temperature. So using the shrinkage rate from the data specification sheets to eliminate film types was in error on my part. ALL Mylar films will heat shrink. Its now just a matter of attempting to determine the particular films heat set temperture. Its critical the temperature a particular Mylar will heat shrink is NOT above the temperature failure level of the attachment tapes!!!
So LAZAIR... you were correct that the advertised shrinkage rates were not important. Those numbers only tell us the nomimal exhibited shrinkage when the material is exposed to heat below the heat-set temperature.
I need to go back over the list and reinstate some films as candidates...
Steve