Daniel, for future reference you might try having the fuselage inverted when you spray the area where the camo meets the black. I know it's a bit cumbersome spraying with the plane upside down but if the tape mask isn't down securely having the fuselage inverted (upside down) will cause any excess paint run off to go AWAY from the tape. That will help to prevent leakage under the tape especially if you are using very thin paint/thinner mixtures.