First, I should make it clear that I've never used fewer than three PS3 Eye cameras, and that was a long time ago. After I upgraded to four (and later six) my results were significantly much better. I would not recommend using fewer than four.
As for camera height, I'm not sure where you got the info about '2 meters minimum height'. Here's is the official info from the Wiki:
http://www.ipisoft.com/en/wiki/index.ph ... cene_SetupBTW, my cameras are staggered at various heights. I think most are about 2 meters, but I think at least one is closer to 1.5 meters and at least one is almost 3 meters high. That said, your own setup may be different depending on the size of your location.