Just thought I'd mention, because of the sidecar and no leading link, I looked at putting a steering damper on, most of the ones I could buy for a bike just didn't have the stroke length I needed for the 13, I ended up getting a steering damper for a VW Beetle, reasonable price and I just had to modify one end with a ball joint, it's dampened in both directions but no adjustment, it worked for me but I've never had any wobble with the chair on so I guess it must be set up well, cheers Pete.
P.S. photo shows the longest stroke bike dampener and the VW one beside it