TR,
That hasn't been my experience. I always trim my helis in normal mode and then switch to idle up. I've never known a discrepancy in trim between the two modes. I use a 9C, possibly your radio is different. What do you use? Side bar: If your swash plate is level you won't need any trim. If you set up your helicopter without leveling the swash, you're in trouble already. A properly setup helicopter shouldn't need any trim. From my experience, idle up effects throttle and pitch curves only. But there are a lot of new radios out there and I could be wrong.....