To improve security and performance, middleboxes (such as firewalls or proxies) may inspect and transform packet contents, delete and inject packets to active flows, and may even reset or terminate entire connections. However, for novel protocols which may not conform to common flow behaviors, middleboxes can interfere with or even block outright the use of these new protocols. In this paper, we present a dual-channel design approach as a way for new protocols to achieve middlebox-friendliness. Under the dual-channel approach, data traffic is sent over a traditional TCP/UDP channel, and additional functionality is accommodated within the payload of a secondary channel. As a case study, we present our prototype implementation of Forward Error Correction for TCP which improves flow completion times by almost 2.5x under 2% loss, despite the overhead of the secondary channel.