As yet another update, I finally got this project finished. The Burley hitch fit on my bicycle, but I couldn't get the the old connector from the Trek to fit. I found this blog post and ordered the Burley square tongue hitch. Unfortunately, it didn't fit in the Trek trailer towbar, which was 1" aluminum square tubing, so I bought a short piece of 1 1/4" aluminum square tubing from W.W. Grainger, slipped it on, and drilled and tapped a 1/4" hole and bolted it for security. I installed the Burley square connector, which was a bit loose, but seems to work okay.
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