Well the protaganists of the change in trim during flight are some well respected jet flyers, they have said that putting Hysol onto the incidence pins to make them solid had cured the changes in trim that they were experiencing, what else can I say, personally I never experienced this, I have also never experienced a lack of elevator authority either, but I do run the C of G well back from that in the manual perhaps that would account for it.

Mike