Your installer is correct about the series vs. parallel issue. Most dual emitters are wired in series. If you are careful you can create this type of hookup with parts from Radio Shack. I see no problem with creating what is essentially a dual emitter with mono plugs just wire them in series so as not to drop your signal strength.

Don't give up on the serial control. It's very reliable and fairly straight forward but you may need to call the manufacturer to find out what they mean by a carriage return.