The only issue you may have with toggling the combiner open is that you could potentially drain your starter battery with your house battery, should you forget to turn it off.
Ok, so I'll post pics when I'm not on my iPad, but here is what I did as far as wiring.
I used an open maxi-fuse slot in the factory installed Blue Sea fuse block, and ran an 8 gauge cable inside split-loom up the port side above the tube. I was able to reach in and zip tie to existing cabling for support. Once I was up as far as the helm, I was able to fish the cable along the cross member to the starboard side right up into the helm. Under the helm I glued in 2 wood furring strips that I screwed a 24" x 20" x 3/8" plywood. This is where I bolted a 400 watt subwoofer amp, a 400 watt 4ch amp for the speakers, the C-100 Combiner, fuse block, and power distribution.
The 8 gauge is connected to the C-100, which charges an Exide AGM Battery. From the battery I used 4 gauge cable to the fuse, and distribution block. From the distribution block I ran 8 gauge to the individual amplifiers.
Photos to come soon.