I am sure the methods described will work.
In a pure dumbass move, I shoved a screwdriver through a 6.5 cone last winter, when building speaker boxes for a friend. I applied a dab of silicone to the cone, let it dry, and all is well. Remarkably, you cannot hear a difference in the car between L and R to determine which driver was violated.
It made me SUPREMELY careful when screwing in drivers since!