I went through the metal just ti the right of my column never had any problems just make sure the wire dosen't rub the side of the hole and short out I had more problems putting on the grommet than the hole itself
there may be a rubber grommet unused in your driver doorjam...the easiest way is to wire through the fender into the grommet and behind the kickpanel...have had mine like that for awhile and no problems (4 gauge) there should be a how-to to the likes of it. otherwise...cars nowadays have pretty blank firewalls..mostly...you should be able to pick out a blank spot and drill through. watch fer lines tho
I FOUND such a simple solution to the power cable problem and it took me all of 10mins. ALL you have to do is run the cable where the factory wires come in from the main fuse box under the hood. It will require removing the drivers side inner fender well..Once you do you will see where the harness goes in and thre is a spot right above or below to drill a hole and install a gromet...DONE... Take a peak inside the car, look under the dash and up...you'll see the factory harness right behind the interior fuse box!!!!!!