Here are some thoughts on senryu that I produced by request for Mike Rehling's Failed Haiku:
http://www.haikuhut.com/Senryū-An-Application-to-be-a-human-by-Alan-Summers.pdf
Also I've just completed my President's report on the 2018 The “AHA” Haiku/Senryu Contest (Annual Hortensia Anderson Memorial Awards) Results, which as it's long, I hope all of it can be included in the United Haiku and Tanka Society newsletter.
If not, I'll certainly add my newest thoughts. :-)