I'm not sure of what @niksmathew has said, but I've heard so else where. What I did and the rest of my friends did were, send our I-20 along with the documents. We treated the I-20 to be "Approval of the Flying school from the state regulatory authority of the period during which training was done" and "Approval of the Flying school from the state regulatory authority of the period during which you went for recency again".
This was more than enough for us as we did not face any problems with it. Though I must let you know, the DGCA will retain your I-20's with them and you shall not get them back.