Tyro,
Thanks.
"THS" - I had realised what it did but I could not work out the TLA
This ensures elevator authority in both directions.
I had not figured out in such clear terms that that was the aim of the trimmer. It was not like that on the C150 or Chipmunk as far as I recall.
Well I am reasonably convinced by myself now, especially after your clarifications.
Very sad if that turns out to be near the case.