First, I'm no expert on this.

But, having followed a lot of the "Jets" stuff over the years, it seems to me that they usually place the pivot point more rearward, say at 40% to 60% chord.

The old Byron kits were that way, with the actuator being in front of the pivot, at about the 20% position.

These numbers are guesses, and I would talk to a more informed jet jockey before adopting my numbers.

Here are some images that might help.