So I installed my Fantastic Fan this weekend. My frustration level was high because the black and white wire that Keystone said was the constant 12v, was in fact not at all a constant 12v. I was able to get a constant 12v from the AC control unit as suggested by another forum member and it worked perfectly. I was able to easily fish the wire across from the AC unit to the vent and the fan worked beautifully. I did have a panic moment though when I went to turn the AC on and my thermostat just gave me an error message. turns out one of the thermostat control wires wasn't in the right spot. Once I fixed that we were golden.
I think the one thing that most of these Fantastic Vent installation videos nee to spend more time on is the wiring. That's really the main issue for most people from what I've read. Putting it on the roof is easy, but making sure you have the right wiring available and that you're hooking in to the right source is a pain in the ass.