RE: Belt CP Spinning Help!
I had the same problem after putting an eflight blade 400 tail rotor shaft (which was a bit longer) on my Belt cp. It wanted to spin around pretty bad at low throttle settings. I think this was because the heli wasnt going fast enough for the gyro to really kick in and make up for the longer shaft which was really throwing the tail rotor blade pitch off. I simply had to slide my tail servo front a bit or back a bit(forget which way) and it fixed the problem right up.
Most likely this is all you need to do. I'm guessing you have to move the servo around to get the pitch of the tail blades about where they need to be when your servo is at its neutral setting. This will make it easier for your gyro to pick up the slack once your start throttling up.
Just spend a minute studying your heli tail rotor blades pitch while considering which way the main rotor blades are trying to spin your heli and then figure out which way to slide your servo. And just make sure your servo arm is centered while your servo is in neutral position. Let us know if you get it fixed!