I went back to the trailer. The friction drive worked just fine but I would have had to strip the electronics from the pusher to get it back to where it used to be. I wasn't quite finished with the pusher yet.
Doc the problem with the trailer seems to be in the hitch. For the bike to handle normaly the trailer has to swing and tilt. And a pull trailer does that very well, the problem comes in when the trailer is powered I think. It it pushes the bike even a little while out of line the rear of the bike takes off and it all begins to fishtail.
When I built the bobtail pusher I didn't have the problem but it was almost impossible to make a right turn. However balance of the bike wasn't an issue since the trailer was always in line with the rear wheel. When the bike leaned the rear wheel leaned. With the two wheel trailer such is not the case.
I have tried several hitch designs and now it is getting closer. The latest incarnation of the hitch is a three point hitch. The main connection more or less lines up with the rear wheel of the bike. then there are two secondary connections from each corner of the trailer to a point farther up the hitch. The hitch is actually a frame that encloses the rear bike wheel. So far it allows for some lean of the bike, which helps with control. It does not allow for very much swing which seems to help. I'm going to keep testing it to see if I can just get used to the way it handles.
I build this one from a ebike I bought off craigs list but they would be easier to build from a 16" bike using both wheels and just weld a #25 sprocket over the bike sprocket so that you could take advantage of the freewheel already in place. I have a couple of motors and mounts that attach to the bile axle and that would work great. It's how I build the bobtail pushers.