XNA WP7 accelerometer Controls

I am porting a game over to a XNA 4.0 WP7 project but am having some problems with controls. I am using the accelerometer to control movement but sometimes the ship will completely skip to another area of the screen. I have the code below for the controls.

    Accelerometer _motion;
    Vector2 accelReading = new Vector2();
    private float speed = 50.0f;

    //Initialize
    _motion = new Accelerometer();

    _motion.ReadingChanged += new EventHandler<AccelerometerReadingEventArgs>(AccelerometerReadingChanged);

    _motion.Start();

    //Method for Changed Readings
    public void AccelerometerReadingChanged(object sender, AccelerometerReadingEventArgs e)
    {
        accelReading.X = (float)e.X;
        accelReading.Y = (float)e.Y;

        vel.X = accelReading.Y * speed;
        vel.Y = accelReading.X * speed;
    }

    //Update
     float elapsed = (float)gameTime.ElapsedGameTime.TotalSeconds;

     pos += vel * elapsed;

     vel *= 1 - elapsed;

ReadingChanged event is marked deprecated in WP 7.1 that's there was some reason and it might be reading errors use CurrentValueChanged.

If that do not help try WP7 using Motion class it is more accure

http://msdn.microsoft.com/en-us/library/microsoft.devices.sensors.motion(v=vs.92).aspx