Have you ever used any "FREE", or "OPEN SOURCE" tool for creating & editing the PCB Stack up ? I am aware of tools such as Polar instruments, but they are licensed tools.
Isola has a very nice stackup calculator. It will calculate layer thicknesses, resin filling and dielectric constant at 1mHz for DE104, DE17, DE156, IS400, IS410, IS420, IS620, PCL370, and FR408.