Game doesn't start when i try using this, at the FTB launcher log this is last entry:
[SEVERE] [Forestry] ic2classic.core.IC2 failed validation. Halting runtime for security reasons. Please replace your mods with untampered versions from the official download sites.
I'm using the 1.6.4 version of IC2 classic and forestry-A-220.127.116.11.jar