A quick post here with more details and pictures to follow (since this has been a hectic summer). The wagon is finally roadworthy! The interior is far from finished but the structural stuff is done. We took it to Echoes in Time last week for its maiden voyage, following a road and stress test earlier. We had a really great time and had many visitors and many great discussions. I was quite surprised at the number of people who knew of other builds.
Towing was far easier than expected even in a fairly strong wind, with the total lack of aerodynamics not appearing to present much of a problem. I kept the speed at 65mph.