Why not use the bike itself as the trailer? Use a dummy front hub as a hitch, remove the front wheel and attach the rest of the bike, running on its rear wheel...
Sounds mad, I know, but I discussed it with somebody at
Watsonian Squire a while ago, and they thought it was a goer. I haven't pulled my finger out and done it, though...
Yikes! You'd think that was a bit iffy in terms of the weight and leverage.
Not really. A bike weighs, what? 12-15kg? The effect of the weight is tiny compared to a 100kg pillion and a 50kg pannier load, say.
I would be cautious of cross winds, though. I notice my 52l top box when it's breezy.