Gearbox Shifting Issue

[Remy G]

Hi, so my team has been experimenting with kicking the ball with a surgical tubing design. We are essentially winding back the kicker by connecting a cord to the output shaft of an AndyMark Supershifter and running it, and then putting the gearbox in neutral(we removed one of the two gears to create a neutral).

The problem is that when we put the gearbox into neutral, the output shaft still has a significant amount of drag on it because there are still 2 or 3 gears engaged. Outside of making a custom gearbox (we don't have much for shop access), what could we do to make the neutral free-spinning? Thank you for the help.