Multi-Viewer 3D Displays (why the 3DS is a handheld divice)

I have been trying to make a, glasses free, multi-viewer 3D monitor (like the Nintendo 3DS, only 23 inch and multiple viewers), and it is much more tricky than it looks.
The parallax barrier cuts down the brightness exponentially based on the number of viewer (50% light cut to do 1 pair of eyes, 75% for 2), so with 2 viewers the screen is dim. But there is more, the resolution is not only cut by 1/4, a pixel is just as narrow, but I am adding a huge gap between them (some test subjects could not even tell what they were looking at)…
Lenticular lenses cost about $12 a foot, but none of the ones I got in the sampler pack line up with the pixels on any of the monitors, so I have to sacrifice even more horizontal resolution…
I gave up and started doing head tracking, but isolating individual eyes on that scale is just about impossible, so I wind up wasting 4X the resolution just to have enough margin for a single viewer…
And it still doesn’t isolate the eyes properly!!!
Now I have a 3D display (if you do not move faster than the head tracking can follow, and remain 2 to 3 1/2 feet from the monitor) that tracks your head, but will not respond to more than 1 viewer…
So I decided that when the head tracking detects more than one person, or if you move around too fast, the character (Tuba-Goose​) will get irritated and leave…
If I can get it to do that, I would consider it a hell of an achievement. And even watching this quasi-3D interface figure out where you are and adjust the perspective  to compensate (with a bit of a lag sometimes) is a little unsettling… Kind of like being eyeballed by a goose…

I can work with this, but I might still have to buy the 3D monitor, or at least the lens that is made for the 23 inch display…