Good advice, everybody
I do like wearing baggy shorts normally, and I hadn't thought about the hazard you mention, Rich.
I like Ron Hill stuff - I used to wear Tracksters to ride for many years. The only drawback was the wind on my back, but that's solved with Bikesters, and even more so by sitting down
I might check out the idea of running shorts. And perhaps rowing shorts too, but...
For now, though, I guess my existing kit is fine