Other than those holes, there is a hole somewhere way up at the top portion a little towards the drivers side from center that the audio shop ran my cable through for my amp. It would be hard to get it through if you ask me...I don't know how they did it.
I've just cut a small X type slit in my rubber boot that goes around the steering shaft and poke wires through that. It's not like anything is gonna get through a small slit anyway and most people won't see it unless they're under your dash anyway.
Just another option...