I'm looking into purchasing a Canon 7d. I'm having trouble finding info on how to work with the in-camera wireless flash options. It looks like the 7d can do e-ttl with ratios for 3 seperate flash groups. I'm trying to figure out if I can still use those 3 seperate flash groups without using the onboard flash. Can the st-e2 unit transmit the cameras data using ir or does it become limited to 2 groups. Also can radio controllers like the Pocket wizard flextt5 or Pixel tr-332 manage 3 seperate groups?