I finished the complete power assist trailer build today. Actually it's a lot like victory in Iraq it is finished but I'm sure a lot of adjustments will be required. I has everything mounted in the trailer. The only thing that runs to the bike is the throttle. I will eventually add a emergency kill switch as well.
I rode the bike. The trailer has to be secured so that it is rigid. Which makes it a lot like a tricycle. You aren't going to have a lot of maneuverability but it is possible to ride it quite comfortably. I plan to take it trail riding as soon as I test the battery pack tomorrow. I have a reading for two miles with just the sla pack. I want to add a nimh pack as well and read the battery results.