I have now switched to a 12/12 cycle and set the ballast 400watts.

The girls also got thier first taste of bloom food today with a mild dose of Pure Blend Bloom.
I have also installed the second fan in my fanbox.These two "vent booster" fans are taking care of the heat from the 400HID with no issues.They are whisper quiet too.
The temps in the cabinet are staying in the low 70's now.I will be looking around for a humidity gauge though,as this may become an issue as time goes on.

Here are some plant pics and the completed fan box.