RE: Stab twist: one side. Effect?
First, did I get the previous stuff close? Or am I completely confused!?
Assuming the plate has no relative mass to affect the CG and what you are envisioning is like a 1'' x 1'' x 1/32 square (like a large trim tab) on a 60 size plane then:
a) if the plate is parallel to the flight path sticking straight back out of the rudder it seems that it would create a stronger effect further from the roll axis causing greater rudder-roll coupling. also, possibly, it would create some drag, offset from the datum line, thereby causing some nose up/climb tendency when the rudder is deflected. (if I got the brick behind the bike analogy correct in understanding you the first time round)
b) if it were placed perpendicular to the rudder then, following again on the drag trying to center idea, would it act as if there were some up trim on the elevator?
yes, no, kinda-sorta?
By the way...Your puppy avatar is adorable...black Labs have been the only type dog I've ever had. just one presently, he's #5