ADAFRUIT 16x24 Red LED Matrix Panel ID:555

Would like to know if there is a way to hook up more then 4 of these boards? I have 4 running without a problem. I was looking around at the forums but see no information about this. Adafruit mention at the webpage: https://www.adafruit.com/products/555 that you can connect 8 of these together. Is someone out there who has(d) success with this?