sniper scope effect "how i did it"

In my opening i have a scene were a Point of view shot is used through a sniper scope to look at the hostage.
this shot wasn't actually taken through a scope or a filter attached to the camera it was in fact an effect I learned after researching how to do it on YouTube.

It was actually very simple all I had to do was take an existing image and play it over the original footage I gathered from researching the effect but my problem was I had to create my own scope so I took a easy image off Google images as a template and designed my own in a bit of Software called "Adobe Fireworks"

 The one above was the original image I used as a template to get an idea how to make my own. my own production is the one below which i made from a series of different shapes and mathematical precision in placing each one to create the sort of scope I was after.

Once I had created my own scope I saved it as a JPEG and transferred it by memory stick on to the Apple Macs which then was converted to a quick time image which I could then upload into final cut pro. in final cut pro it was simple all I had to do was place the image above the original footage in a separate video play bar and then select the positioning of the scope to get the area I want visible in the scope.

The image works because the white inside it does not play in the film and when another bit of footage is played at the same time it replaces the white with that footage and wear as the black cancels out the footage. both of these create the effect I am after which is my sniper scope shot.