Running amp power through firewall grommet... '95 Grand Marquis?

I'm trying to figure a way through the firewall. There's a rubber grommet under the glove compartment that looks like it's big enough, but after I pull it out I noticed that the back is shaped like a cone with the wires in the middle. Would it be possible (and safe) to drill a hole into the grommet to run the 1/0 gauge wire through? It's pretty thick rubber.
 
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