[joelg236]

In this :

public void teleopPeriodic() {
        if (control.getRawButton(1)){ // if button 1 pressed drive at full speed
            driveSys.tankDrive(control, 2, control, 5);
        }else {                       // else drive at half speed 
            driveSys.tankDrive(control, 2, control, 5);
            driveSys.setMaxOutput(0.5);
        }
    }

Make sure you setMaxOutput() back to 1 when the button is pressed. So,

public void teleopPeriodic() {
        if (control.getRawButton(1)){ // if button 1 pressed drive at full speed
            driveSys.tankDrive(control, 2, control, 5);
            driveSys.setMaxOutput(1);
        }else {                       // else drive at half speed 
            driveSys.tankDrive(control, 2, control, 5);
            driveSys.setMaxOutput(0.5);
        }
    }