Huh, does Haunting of Hillhouse == House on Haunted Hill?
I know the latter was a remake of an older film which I never saw. I remember really liking that movie when it came out, but that was a long time ago now, it may have simply been good compared to the garbage that was standard at the time. I should watch that again.

Anyway,
I'm not sure what I would want the intent of the experiment to be. I have a couple of ideas, but nothing solid.
The purpose could be to discover the general line past which most people begin to develop trauma-related disorders.
It could be to double-cross their mole/agent into revealing the location of an HVT he helped go into hiding.
It could be that the research group is being funded by an eccentric billionaire with nothing better to do than go out of his way to scare some people.

I'm not sure...

I would like to see the experiment get out of hand. I'm thinking that maybe the history of this particular tropical island involves a Spanish stronghold for silver and gold which was raided by privateers. Women, children, the whole structure and all soldiers wiped out before a storm blew through and trapped the privateers on the island where they all eventually died as well. Maybe the group or the researchers stir up the pain, anger and fear of these spirits unwittingly.