It was key that I got each item in the right place. The bottom layer is the footage, the second from bottom layer is the bin with its shadow, the third from bottom layer is the monster with its shadow and the top layer is the mental ray tiff sequence of the bin and the monster.
I then changed the opacity of the shadows to making them both lighter and keep the bins shadow slightly darker than the shadow from the monster. With changing the opacity of the shadows I found that subtlety was the key.
I then added an Gaussian blur to the shadows, so that they didn't look so defined. Then to the mental ray tiff sequence of the bin and the monster I added the effect CG force motion blur, this would add more realism to the movement of the bin and the monster in the shot.
It was then just a case of tweaking the opacity, the Gaussian blur and the CG fore motion blur in order to create the most realistic effects. I used the shadows that were already cast in the footage and the motion blur that appears from the Parkour character in the footage as reference. This helped me to get the shadows and motion and Gaussian blur just right. Once I was happy with everything it was them time to render.
I then did exactly the same process for shot 8, except all I had to do this time was change the opacity of one shadow, and add Gaussian blur to it, and then add CG force motion blur to the mental ray tiff sequence of the bin. Again tweaking it afterwards so that it fitted with the real life footage and then rendering it out once finished.
Below are some images that show how I composited the shots in after effects.
Below are images of the render settings that I used for rendering out with after effects. Rendering took a very long time!
Below is the video of my completed composited shot 7.
Below is the video of my completed composited shot 8.
Overall I am extremely happy with how the two shots that I composited turned out. I think that the CG fits in fairly well with the real life footage and looks a lot better than I initially thought it would.