I had that exact same question when my 20120 came in. And it looks like someone else has that question too:
http://www.rc-monster.com/forum/showthread.php?t=2643.
As to soldering the wires together and then to another wire (like a "Y"), I'd use some 10 or 8 gauge wire easily available from any car stereo shop. That's actually a good idea if it's done right.
Once a method is worked out, maybe sticky it?