Step 6: Finished images
A threaded bar instead of a pivot would be a simpler mounting and would allow fore and aft adjustment of the sidecar position - although this would not be as quick to release.
The sidecar could have been a little longer to give more growing room. It was designed to fit in the boot of our car, but longer would have been better.
The wheel mounts could have had slot which was open at the Bottom. This would give the simplest wheel removal without the need to unbolt the outer frame part.
More sidecar details can be found at : http://www.steves-workshop.co.uk/vehicles/sidecar/sidecarindex.htm