I did it myself, as well as played around with various sub woofer installs.
Its basically 2 wires to the top of the IMA pack and a conenction to ground up front and I tapped the accessory fuse for power. A switched when in a blank on the dash to turn it off and on.
I found the Insight was touchy unlike the CRZ to extra power in the syste, so I turned it off and on at lower speeds and left it on above 45 mph. I also found if I left the blower on fan speed 3 it allowed me to use it at lower speeds without triggering an IMA error. It was easy to reset by turning the key off and on. Even at 117 volts and 17 amps it was fairly easy in ev mode to suck the charge down, so I would also use it to recharge the ima pack before plugging in or going on another leg of a trip. When I would park at a store I would sit for a few minutes watching the soc screen for the battey to fill up before turning everything off and going inside.
This is back when I got 103mpg.
Abuse of ev mode