Hi nick!
There is a step you miss:
You have to connect one by one every power adjust to the pc via USB cable, open aquasuite 2012 Beta 15, update the PA to the 1004 firmware, assign a diferent aquabus channel to every PA (50 for the fist, 51 for the second...).
After that, you can connect the 3 PA to the aquaero via the aquabus in the way you describe. You will see 3 more FANs, 3 temp sensors and 3 flow sensors in aquasuite.
The aquabus only uses 3 cables, no problem with that.
Wish this will help you.
regards!