I discovered a good use for Hard Light Transparency

While Gene and I like to think of stereograms as an art form we have been working on for almost 30 years to perfect, many stereogram enthusiasts don't care about technique, they just want to see the hidden object. IOW to them it's a just puzzle.

With AI generated images and AI created depth images, it is possible to have a larger image that is visible but at the same time produces a 3D image. But this disappoints some stereogram viewers because they want to solve the puzzle.

After some experimenting, I hit on using a Hard Light Transparency at 50%. This adds a surprising amount of detail to the hidden image without making it immediately obvious what the hidden image is.

The first image is just the basic stereogram. You can see a hidden shape but it is not easy to tell what it is. The second image shows the larger image and you can tell what the image is in 2D. The overlap of the image as it repeats cuts down on the clarity somewhat. The third image has the Hard Light transparency and makes the detail and shape of hidden image much easier to see. On the bottom is the same image, flopped. Because it is smaller there is less overlap and the images are clearer.

I can see the hidden shape in the first stereogram but as you state without a reference image it's very hard to say it's a helmet.
There's to much overlap in the second and the third is far better but I still like to see a clear 3D effect which is fantastic in the final render of the lower helmets.