Xamarin Forms Frame Shadow Design

I have implemented something very similar (also Frames as cards to be displayed in a stack view). Unfortunately I can't share the exact code, for it's not me owning it, but my employer, but I can tell you how to achieve this.

I have added a property ShadowRadius to CardView and created a custom renderer, derived from Xamarin.Forms.Platform.Android.AppCompat.FrameRenderer. In the renderer I am setting the Elevation of the renderer

protected override void OnElementChanged(ElementChangedEventArgs<Frame> e)
{
    /* ... */

    this.Elevation = ((CardView)e.NewElement).ShadowRadius;
}

My cards are showing a nice elevation shadow with Xamarin.Forms 2.5.0.280555.