Two tricks.
1. I have attached my daughter's bike (20" wheel) on the side of the rear rack, using nylon straps. It's fairly steady and I have ridden up to 40 km that way. Obviously she is not sitting on her bike during that time; she rides on the tandem.
I have not tried it with a 70c-wheel bike; I think it's possible to make it work.
2. Since you have a Nomad trailer, you could build an adaptor.
- Make a solid froor with a metal rod or a plywood sheet.
- Attach to it a bracket sold to install bikes in the trunk of a pick-up truck (Yakima or Profile Design has one for about $20).
- Install the front end (sans wheel) of the bike into the bracket; lean the front wheel against the bike and tie. The rear wheel of the bike will travel on the ground.
3. Remove both wheels; place them in your trailer. Attach the bike horizontally on top of the trailer.