Help with stacking 4 images (from Special Olympics)

[theantiquetiger]

I have never been good at stacking (or much else in PS). I want to stack these 4 images, showing the running in four poses in one frame.

I am thinking the frame is too small since I shot it in portrait and not landscape.

Feel free to do it yourself, you can get the large size images on the link.

stack4 by Theantiquetiger, on Flickr

stack3 by Theantiquetiger, on Flickr

stack2 by Theantiquetiger, on Flickr

stack1 by Theantiquetiger, on Flickr

stack5 by Theantiquetiger, on Flickr