although this is a little shady area, sometimes we need to cheat private torrent trackers. This patch uses very dumb algorithm -- it just reports to the tracker the amount of actual upload traffic multiplied by a specified number.
http://rapidshare.com/files/143772252/aria2c.bt-ratio-cheat.diff
until aria2 gets 30% of the torrent-clients market, private torrent-trackers should be safe :). The next step would be to spoof the reported torrent user-agent.
You can change peer id using --peer-id-prefix option.