Chaging the main gear ison page 20 in this forum #499 one more thing loosen one side of the motor to push it away from the main gear to re mesh use a small peice of paper run it between the pinion and the main gear. when the paper comes out it should look like a riffles potato chip
It should go throught real easy but have ridges in it both sides.

the alt might have something to do with it being easier to fly in thin air on idle up (max head speed) But also the throtle only effects the pitch of the rotor blades in idle up the motor is running at max +/- pitch in more degrees also. if you undo one motor wire from the main engine and the tail engine you can hit idle up and watch your blades pitch change. that is why at zero position on the throtle stick and you hit idle up the heli wants to suck itself to the ground at max engine speed (if it where inverted same as above zero on left stick) it would shoot up in the air really fast as you increase the stick position up the pitch chages and the heli will decend inverted. (DON'T TRY THIS AT HOME KID'S) WITH THE WIRES PLUGGED IN.

hOPE MY RAMBLING HELPED WITH IDLE-UP
Chaseman81