Kolarshooter, there is no spooling up and down. When in heli idle up mode the throttle is controlled by a "curve" in the radio relative to throttle position. The pitch is also controlled by a curve relative to the throttle stick as well. In aerobatic heli, the throttle curve looks like a V. At low stick you get full throttle, at high stick you get full throttle. At mid stick, the ideal is to be able to maintain the same RPM that you get with full throttle and full pitch(either forward or backwards pitch). So, ideally the prop speed never changes in idle-up. The name idle-up confuses a lot of people because it has nothing to do with idle. On a heli radio, you have several idle-up modes. One mode can be set so that the plane would act like a regular fixed pitch plane. When I get one of these, I will likely set a mode so that I can spool up the blades but they won't have any pitch to them. I will move the throttle to mid stick and then switch to idle-up1 that will have the full range of pitch curves. Since I do it at mid stick, there won't be any pitch in the blades in either mode so it won't move. Now the motor will be at full speed and the throttle stick will control the pitch. You won't want to push a button and slam in full negative pitch. It would be very destabilizing to the airplane. You will also want to have a throttle hold switch set to kill all power to the motor no matter what mode you are in. This is to "save" the hardware in a wreck. With a normal plane you just pull the throttle to idle in a wreck. With VPP that would send it to full throttle reverse pitch. While it may lessen the impact, it's going to continue to beat the snot out of the plane till you gather your wits enough to get out of idle up and shut off the motor. After flying helis several years, at the first sign of trouble, I flip the throttle hold switch. I talked to Scott Foster at the JR Indoor fest in Columbus and this is his basic setup as well.
Matt