Did you get it figured out?
If not, if you look at the front of the booster, it comes out on the lower left side of it. There is also a rubber ring in the firewall hole to help seal it. If you take it out you can fit quite a bit through there. Right now, I have a 4gauge, 8guage, and a few 16guage wires running through it along with whatever existing was there (can't remember if there were though).
Any pics?