How does the wifly flush work?

I m using a wifly module to transmit a total of 7200 bytes. This is broken down into 1440 chunks as this is the limit to the buffer size.

For the most part this is reliable using a flush timer of 1s and a flush size of about 1440 bytes. However when the wifly module is located

in areas where there is less signal the full 7200 bytes are not received. Only about 4320 bytes get received. My question is regarding the

way the flush works. If you flush a second time before the first flush has arrived at its destinaion will this overwrite the initial flush.

If so how do you work around this problem. Is there a way of confirming on the wifly that bytes have properly sent before sending the next

batch? I have played around with flow control by varying the buffer size and flush timer but I think this wont solve the problem for the lag

in poor wifi reception when further away. Can the wifly detect if bytes are definitely sent and ready for the next flush?