I wired the head and it works beautifully. The only catch is that I ran 16 gauge to the unit, and after I installed it I read the instructions (that's the arrogance of a nerd there, installing something before reading the manual) and it specifies 8 or 6 gauge should be used. There's no way I'm running that thick a wire to and from my panel, and that doesn't make sense when the panel's wired with 12 gauge anyway. Instead, I'm going to run 6 gauge from the battery directly, controlled by a solenoid which is actuated by the switch on my panel.
One problem I had to solve was that the new panel does not have built in fuses (I did this on purpose) and is significantly larger than the old. At the same time, I'm adding more electronics (AIS receiver, thermostat, refrigerator control, etc) that needs somewhere to live. To address this, I decided to hide all the electronics in one of the J/30's four main cabin cupboards, behind sliding plastic doors. So my dad built a backing wall within the space, and I mounted the electronics on one side and the fuse boxes on the other, with all loads terminated at the fuses. It's starting to look pretty nice: