Interaction between Heightened Invisibility and Ventriloquism

[Atalius]

Anyone know how the following would interact. If I was able to cast Ventriloquism and Heightened invisibility beforehand and I was Casting a spell say like Phantasmal Killer against a monster (which would normally give away my location from undetected to hidden) would I be able to use Ventriloquism to remain undetected? What would the enemy's Perception check be against?

Heightened Ventriloquism (2nd): The spell's duration increases to 1 hour, and you can also change the tone, quality, and other aspects of your voice. Before a creature can attempt to disbelieve your illusion, it must actively attempt a Perception check or otherwise use actions to interact with the sound.

[Kennethray]

So invisibility would hide the somatic hand movements, ventriloquism can make the sound of the verbal seem 60 feet away. What about the obvious gathering energies around where you are casting? If you have none of the feats that get rid of that, then at best I would say you become hidden but also there would appear to be a second one of you 60 feet away.