How to get Picture in Picture to slide in

Ok, so I am using iMovie 10.0.5.

I am using the Picture in Picture effect for a PNG photo.

Is it possible any how to get the photo to slide in to the video instead of any of the other transitions?

I have tried doing this using the Side by Side effect, but black bars appear either side of my image and because it splits it in the center it cuts off the subject of my video.

Any ideas would be appreciated. Thank you!