use netcat to pipe vnc, or radmin, to a listened port already open, like 80, and use fpipe to port 80, you will resive more packets if there using the internet(browsing) but you wil also grab the vnc server, and they wont know the different.
just take in mind if there downloading files tro the browser you will recive that packet as well, eg a 70 meg file and they started it 5 minutes ago, u will get adlest %80 of the download if there on adsl.
but its a considered easy way away from a firewall, and a nice reverse connection key....PS why do u wanna reverse back :S unless your leeching