Hi sheppey,
I don't understand the "full rudder trim" point. What aircraft type are you referring to?
A320. From FCOM below:
"If Buffet:
The warning alone, without buffet or vibration, may be a false warning.
MAX SPEED... 240 KT
ENG MASTER... (affected engine) OFF
If reverser is actually deployed:
RUD TRIM... FULL R (L)
CONTROL HDG WITH ROLL"
In Normal Law, it may be due to fact there is no feed back through side stick of the amount of aileron required and possibility of running out of aileron authority unless lots of rudder is applied.