Thanks Joel ,that clears things up a bit
in my days of rudder only towline A1 & A2s the deepening dive was a well known problem ,
shallow dives have always been my personal use, and power off to trim for best glide then apply power to observe what power thrustline trim is needed, but I have always found the more power/speed the more adjustment needed.
I have also had two aircraft that flew best with the cg right on the leading edge
and that confused the heck out of me.