Amplifier wiring advice needed!

[Nesh]

Hi all

I'm at that joyful stage of adding a subwoofer to the ds3 the problem I face however is that I'm using 4 AWG wire to provide power to the amp but I can't figure out how to route it to the boot. I've tried the methods mentioned on the guides but my wire is too thick to go through the grommet for the washer pipe any ideas on how else to route it to the back. Any suggestions would be appreciated! 

[cyclone]

Drill a hole, treat the edges to prevent corrosion, add a grommet, and go drink a beer