What do you mean that when you have the transmitter in Mode I, the trims are backwards? Do you mean that when you change to Mode I, and, say, the elevator servo moves clockwise when you move the elevator stick to the "up" position, that when you reverse the channel in the transmitter so that the elevator servo then moves counter-clockwise for "up", adding trim for "up" makes the servo move clockwise? That would not be correct, of course. When you give "up" elevator, moving the trim in the same direction as the stick should make the servo move in the same direction.

Please give us some more clarification. What is actually happening?