Connecting multiple Arduino Mega ADK

Hello Guys,

I have a project where I want to control multiple serial devices using mobile phone. I have android based phone with Android 2.3.4 (which supports
Open Accessory APIs:http://developer.android.com/guide/topics/usb/adk.html)

This i can run an application on my phone which controls the Arduino Mega ADK. http://store.arduino.cc/ww/index.php?main_page=product_info&cPath=11_12&products_id=144 This board has 4 serial ports but i have 6 devices(may be more) so i want to connect multiple Arduino Mega boards. is it possible?

So in my project following are three main entities.

  1. Mobile Phone (Acts as USB Client but has special Open Accessory API through which it can talk to Arduino Mega Master)
  2. Master Arduino Mega ADK (Acts as USB Host and accepts commands from Mobile Application)
  3. Slave Arduino Mega ADN (Acts as Slave Arduino Mega which accepts commands from Arduino Master)

Please let me know if this is possible.

Thank You,
Parin