Idle up mode on the B400 is what eflite calls stunt mode in the manual. Now a lot of people learning are not ready for stunt mode untill after much practice. I have slowly been learning on my B400 and have been in stunt mode several times. Best not to flip that switch when flying in a confined area because your head speed with immediatly accelerate and the heli may rocket skywards, watch out for low ceilings. An increased head speed is common for idle up flying and makes the helicopter much more responsive. On the B400 stunt mode you will also have much more negative pitch available for doing inverted flying and 3d manuvers. I believe the increased head speed and a more responsive helicopter is what they were trying to direct you towards. What I have done for flying indoors this winter is to drastically reduce my throttle curve for stunt mode. Out of the box your mid point throttle is at 90% with 100% on each end of the curve. I have decreased mine to 75% mid point and 80% on the ends points keeping a nice bell shaped curve. So I can start to fly my helicopter and she will lift of around half throttle then I flip the stunt switch and head speed increases which gives better control response for flying around the gym. Please remember when in stunt mode and you pull back on the throttle the blades keep spinning at the high speed and your pitch response is also increased so the heli will hit the deck fast. Just practice being quick on the stunt mode switch and maybe just use it for short durations to get started. You might even want to board the helicopter to the ground and see how all this works before doing it in the air. Well anyways I hope this helps and good luck learning with your B400!