Chopping / doubling balls with a '02 Rebel VTL or Bottomline? Try these steps:
1) Turn your powerfeed to the off position.
2) Clear the breech of paint balls.
3) Fill the power feed with the paint you want to use.
4) SLOWLY! Turn the power feed knob COUNTERCLOCKWISE!!! until the balls start to feed easily but not wide open.
5) Rapid fire the gun.
6) Repeat steps 4 & 5 until reliable feeding without chopping / doubling occurs.
long winded explanation why this works.... email me if you want it