So what is the next step?
If you could fit a good brake to the trailer axle, probably a disc brake, with the brake stay connected to an appropriate sized load cell, you could make it into a dyno. Just connect the master cylinder on the bike to the brake cylinder to add the necessary drag. I think Brent DeStoop (sp.?) did something like that down in Australia, but I can't find the photo. There would be lots of heat to deal with, but a Nascar type brake blower might allow short blasts.
Tom